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Questions and Answers

According to the TEMPO group, what is the minimum duration for a condition to be considered predominant?

half of the forecast period

45 consecutive minutes

less than 30 consecutive minutes

30 consecutive minutes (correct)

What is the purpose of the extra 15 minutes in the exception for thunderstorms?

To give forecasters extra time to respond

To allow for increased safety measures

To provide for the 15-minute period between the time thunder is last heard and the time the thunderstorm is officially ended (correct)

To account for the time it takes to issue a warning

What happens to forecast conditions preceding the FMYYGGgg group?

They are used as a reference

They are ignored

They are replaced by the conditions forecasted in the FMYYGGgg group (correct)

They are combined with the conditions forecasted in the FMYYGGgg group

When is a four-digit time in whole hours (e.g., 1600) still acceptable?

Only in the FMYYGGgg group Signup and view all the answers

What is the purpose of the YYGGgg format in the FMYYGGgg group?

To indicate the beginning of a self-contained part of the forecast Signup and view all the answers

What happens when the conditions in the TEMPO group last more than 30 consecutive minutes?

The conditions are considered predominant Signup and view all the answers

What is the main difference between the FMYYGGgg group and the BECMG group?

The FMYYGGgg group indicates a change in weather conditions, while the BECMG group indicates a beginning Signup and view all the answers

What is the purpose of the YY and GG indicators in the TEMPO group?

To indicate the start and end of a forecast period Signup and view all the answers

What is the purpose of the Forecast Volcanic Ash (VA) in the weather forecast?

To report the presence of volcanic ash as present weather regardless of visibility restrictions Signup and view all the answers

What is the minimum wind speed required to report a Squall (SQ) in a weather forecast?

22 knots Signup and view all the answers

How are the cloud groups arranged in the Cloud and Obscuration Group (NsNsNshshshsCC)?

In ascending order of cloud bases AGL Signup and view all the answers

What does the abbreviation 'SKC' represent in the Cloud Amount (NsNsNs)?

Sky clear Signup and view all the answers

What is the purpose of the summation principle in the Cloud Amount (NsNsNs)?

To state that the sky cover at any level is equal to the summation of the sky cover of the lowest layer Signup and view all the answers

What does the encoding 'VVhshshs' represent in the Cloud and Obscuration Group (NsNsNshshshsCC)?

The vertical visibility in hundreds of feet when the sky is totally obscured Signup and view all the answers

What is the definition of a ceiling in the Cloud and Obscuration Group (NsNsNshshshsCC)?

The height above the earth's surface of the lowest layer reported as broken or overcast Signup and view all the answers

What is the unit of measurement for the height of the base of the cloud layer (mass) in the Cloud Amount (NsNsNs)?

Hundred of feet Signup and view all the answers

What is the sequence of elements to consider when constructing predominant forecast weather (w'w') groups?

Intensity, proximity, description, precipitation type, obscuration Signup and view all the answers

What is the maximum number of w'w' groups that can be included in a forecast situation?

3 Signup and view all the answers

What takes precedence over all other w'w' groups when applicable?

Funnel clouds (FC) and tornadoes (+FC) Signup and view all the answers

When encoding VC, where should it be placed in relation to the precipitation, obscuration, or other weather phenomena entry?

Before the precipitation, obscuration, or other weather phenomena entry Signup and view all the answers

What is the correct encoding for forecast weather in the vicinity?

As the last entry in the weather (w'w') group Signup and view all the answers

When an encoded predominant forecast condition is followed by a change group without a w'w' group, what should be encoded?

NSW (no significant weather) Signup and view all the answers

What is the purpose of limiting the w'w' group to three groups?

To ensure that only significant weather conditions are included Signup and view all the answers

What is the correct encoding for thunderstorms without precipitation?

+TS Signup and view all the answers

What is the primary purpose of the icing group in forecasting?

To forecast icing not associated with thunderstorms Signup and view all the answers

How is the type of icing encoded when forecasting more than one type of icing within the same layer?

The highest code figure is encoded Signup and view all the answers

What is the unit of measurement for the height of the base of the forecasted icing layer?

Hundreds of feet AGL Signup and view all the answers

What is the purpose of the turbulence group in forecasting?

To forecast turbulence not associated with thunderstorms Signup and view all the answers

What category of aircraft is the turbulence forecast applicable to?

Category II (CAT II) aircraft Signup and view all the answers

What happens when forecasting a layer to be thicker than 9,000 feet?

The layer is repeated so that the base of the layer coincides with the top layer Signup and view all the answers

What is the format of the turbulence group?

5BhBhBhBtL Signup and view all the answers

What is the purpose of the 'h' symbol in the icing group?

To indicate the height of the base of the forecasted icing layer Signup and view all the answers

What is the primary source of VA plume forecasts if the responsible VAAC cannot produce them?

Air Force forecasts Signup and view all the answers

What is the height encoded in the VA group in hundreds of feet?

Above Ground Level (AGL) Signup and view all the answers

When forecasting VA to be surface-based, what should be encoded in the TAF?

VA as both present weather and add a VA group Signup and view all the answers

What is the purpose of the Non-Convective Low-Level Wind Shear Group (WShxhxhx/dddfffKT)?

To forecast wind shear not associated with convective activity Signup and view all the answers

What is the format for encoding non-convective low-level wind shear forecasts?

WShxhxhx/dddfffKT Signup and view all the answers

What is the indicator for the Low-level wind shear group?

WS Signup and view all the answers

What is the height of the top of the volcanic ash layer encoded in?

Hundreds of feet Above Ground Level (AGL) Signup and view all the answers

What is the rule for encoding the height of the base of the volcanic ash?

Encode in hundreds of feet Above Ground Level (AGL) Signup and view all the answers

What is the primary purpose of the Air Force Terminal Aerodrome Forecast (TAF) code?

To provide weather forecasts for aviation safety Signup and view all the answers

What is the radius of the area in which forecast elements in the main body of the forecast text apply?

5 statute miles Signup and view all the answers

What is the purpose of the VC encoding in the TAF code?

To specify weather conditions greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center Signup and view all the answers

What is the TAF code format derived from?

International standards established by the World Meteorological Organization Signup and view all the answers

What is the main difference between the TAF code and the METAR code?

The TAF code is used for forecasting, while the METAR code is used for reporting current weather conditions Signup and view all the answers

What is the purpose of the TAF encoding?

To provide weather forecasts for aviation safety Signup and view all the answers

What is the format of the TAF code?

FMYYGGgg Signup and view all the answers

What is the reason for limiting forecast elements to a 5 statute mile radius of the aerodrome?

To ensure aviation safety Signup and view all the answers

What is the sequence of elements to consider when constructing predominant forecast weather (w'w') groups?

Intensity/proximity, description, precipitation type, obscuration, or other weather phenomena Signup and view all the answers

What is the maximum number of w'w' groups that can be included in a forecast situation?

Three Signup and view all the answers

What takes precedence over all other w'w' groups when applicable?

Funnel clouds and tornadoes Signup and view all the answers

When encoding VC, where should it be placed in relation to the precipitation, obscuration, or other weather phenomena entry?

Before the precipitation, obscuration, or other weather phenomena entry without a space between Signup and view all the answers

What is the correct encoding for forecast weather in the vicinity?

No specific encoding is required Signup and view all the answers

When an encoded predominant forecast condition is followed by a change group without a w'w' group, what should be encoded?

NO SIGNIFICANT WEATHER (NSW) Signup and view all the answers

What is the purpose of limiting the w'w' group to three groups?

To prioritize the most significant weather conditions Signup and view all the answers

What is the correct encoding for thunderstorms without precipitation?

TS Signup and view all the answers

What is the correct encoding for wind direction in the non-convective low-level wind shear forecast?

In tens of degrees true, with the indicator 'WS' Signup and view all the answers

What is the correct indication of wind speed in the non-convective low-level wind shear forecast?

Knots, with the indicator 'KT' Signup and view all the answers

Where is the non-convective low-level wind shear forecast included in the TAF?

After the cloud forecast and before the altimeter setting forecast in the initial forecast period Signup and view all the answers

What happens to the non-convective low-level wind shear forecast once included in the TAF?

It remains the prevailing condition until the next FM or BECMG group or until the end of the forecast valid period Signup and view all the answers

What is the unit of measurement for the wind speed in the non-convective low-level wind shear forecast?

Knots Signup and view all the answers

What is the correct format for encoding wind direction and speed in the non-convective low-level wind shear forecast?

WSdddfffKT Signup and view all the answers

What is the purpose of the non-convective low-level wind shear forecast in the TAF?

To forecast wind shear below 1,500 feet Signup and view all the answers

What is the height above which the non-convective low-level wind shear forecast is not included in the TAF?

1,500 feet Signup and view all the answers

What is the minimum variability in wind direction required to encode the limits of variability in the remarks?

60 degrees Signup and view all the answers

What is the correct encoding for wind speed when it is 6 knots or less and a direction cannot be determined?

VRBff Signup and view all the answers

When should the wind direction be encoded as VRB?

When forecasting a prevailing wind direction is not possible Signup and view all the answers

What is the minimum increase in wind speed required to encode gusts?

10 knots Signup and view all the answers

How should the peak gust direction be encoded when it can be forecast but the prevailing direction cannot?

In the remarks Signup and view all the answers

What is the unit of measurement for wind speeds in the wind group?

Knots Signup and view all the answers

How are wind speeds encoded when they are equal to or greater than 100 knots?

In three digits Signup and view all the answers

What is the time constraint for the forecasted conditions to occur in the TEMPO group?

Less than 30 minutes Signup and view all the answers

What is the purpose of the icing group in forecasting?

To forecast icing not associated with thunderstorms Signup and view all the answers

What is the unit of measurement for the height of the base of the forecasted icing layer?

Hundreds of feet AGL Signup and view all the answers

When forecasting a layer to be thicker than 9,000 feet, what should be done?

Repeat the icing group so that the base of the layer expressed by the second group coincides with the top layer given by the first group Signup and view all the answers

What is the format of the turbulence group?

5BhBhBhBtL Signup and view all the answers

What category of aircraft is the turbulence forecast applicable to?

Category II (CAT II) Signup and view all the answers

How is the type of icing encoded when forecasting more than one type of icing within the same layer?

The highest code figure is used Signup and view all the answers

What is the purpose of the turbulence group in forecasting?

To forecast turbulence not associated with thunderstorms Signup and view all the answers

When encoding the height of the base of the forecasted icing layer, what table is used?

Table 1.4 Signup and view all the answers

What is the primary purpose of issuing an amendment (AMD) to a TAF?

To provide an updated forecast for the remaining valid period Signup and view all the answers

What is included in the entire original text of the TAF when issuing a correction (COR)?

The entire original text, with only the erroneous elements changed Signup and view all the answers

What is the purpose of the Four Letter Location identifier (CCCC) in the TAF message heading?

To identify the aerodrome location Signup and view all the answers

What is updated for each change to a TAF, including amendments and corrections?

The issue date and time Signup and view all the answers

What is the format of the issue date and time in the TAF message heading?

YYGGggZ Signup and view all the answers

What is the purpose of the valid period (YYG1G1/YYG2G2) in the TAF message heading?

To define the time period covered by the forecast Signup and view all the answers

What happens to forecast groups that are no longer valid when issuing an amendment (AMD) to a TAF?

They are removed from the amended TAF Signup and view all the answers

What is the format of the message heading in a TAF?

TAF [AMD or COR] CCCC YYGGggZ YYG1G1/YYG2G2 Signup and view all the answers

What happens to the forecast conditions preceding the FMYYGGgg group?

They are superseded by the conditions forecasted in this group Signup and view all the answers

What is the purpose of the four-digit time resolution in the FMYYGGgg group?

To provide a higher time resolution for forecast and amending events Signup and view all the answers

What happens when the conditions in the TEMPO group last more than half of the period indicated by the time YYGG to YYGeGe?

The temporary condition is considered to be predominant and entered in the initial forecast period Signup and view all the answers

What is the purpose of the exception for thunderstorms in the TEMPO group?

To allow for 15 minutes of additional time for the thunderstorm to end Signup and view all the answers

What is the format of the time indicator YYGGgg in the FMYYGGgg group?

Two-digit date and four-digit time Signup and view all the answers

What is the purpose of the YY and GG indicators in the TEMPO group?

To indicate the start and end of the temporary condition Signup and view all the answers

What is the consequence of the conditions in the TEMPO group lasting more than 30 consecutive minutes?

The temporary condition is considered to be predominant and entered in the initial forecast period Signup and view all the answers

What happens to the forecast conditions when the FMYYGGgg group is used?

They are superseded by the conditions forecasted in this group Signup and view all the answers

Between 011800Z and 012100Z, what is the wind direction and speed?

140 degrees at 12 knots Signup and view all the answers

Between 012145Z and 012400Z, what is the sky cover?

Overcast at 3000 feet Signup and view all the answers

Between 012300Z and 012400Z, what is the lowest altimeter setting?

29.83 inches of mercury Signup and view all the answers

Between 020100Z and 020300Z, what is the visibility?

200 meters Signup and view all the answers

Between 020100Z and 020300Z, what is the type of icing?

Moderate clear icing Signup and view all the answers

What is the forecast minimum temperature?

-01°C Signup and view all the answers

Between 012145Z and 012400Z, what is the weather condition?

No significant weather Signup and view all the answers

Between 011800Z and 012100Z, what is the ceiling?

600 feet Signup and view all the answers

What is the purpose of including the cumulonimbus (CB) contraction in the TAF forecast?

To indicate the presence of thunderstorms in the vicinity Signup and view all the answers

What is the unit of measurement for the visibility in the TAF forecast?

Meters Signup and view all the answers

What is the lowest altimeter setting indicated in the TAF example in Figure 1.3?

30.01 inches of mercury Signup and view all the answers

What is the sky cover indicated by the 'FEW' contraction in the TAF forecast?

Few, scattered, or broken Signup and view all the answers

What is the wind direction indicated in the TAF example in Figure 1.3?

030 degrees Signup and view all the answers

What is the purpose of the 'TEMPO' group in the TAF forecast?

To indicate a temporary change in weather conditions Signup and view all the answers

What is the time period indicated in the TAF forecast in Figure 1.3?

011600Z to 022200Z Signup and view all the answers

What is the purpose of the 'BECMG' group in the TAF forecast?

To indicate a permanent change in weather conditions Signup and view all the answers

What is the unit of measurement for the height of the base of each sky cover layer in the aerodrome forecast?

Hundreds of feet Signup and view all the answers

What is the only cloud type included in the aerodrome forecast?

Cumulonimbus Signup and view all the answers

When forecasting a surface-based partial obscuration, how should it be encoded?

As FEW000, SCT000, or BKN000 as appropriate Signup and view all the answers

What is the purpose of including the amount of partial obscuration in the sky cover summation computation?

To provide a complete picture of the sky conditions Signup and view all the answers

What happens when two or more significant sky conditions alternate frequently from one to the other?

Use a variable sky condition remark Signup and view all the answers

How should the height of the base of each sky cover layer be rounded when it is less than 50 feet?

Down to 000 feet Signup and view all the answers

What is the purpose of the reportable cloud layers defined in Table 1.3?

To provide a standardized way of reporting cloud heights Signup and view all the answers

What is the correct format for encoding the height of the base of the cloud layer when it is greater than 5,000 feet but less than 10,000 feet?

To the nearest 500 feet Signup and view all the answers

What is the reportable value for a visibility of 3700 meters according to Table 1.1?

3400 Signup and view all the answers

When is a weather and/or an obscuration (w'w') included in the forecast?

When visibility is forecast less than 9999 meters Signup and view all the answers

What is the reportable value for a visibility of 4800 meters outside the Continental United States (OCONUS) locations?

5000 Signup and view all the answers

What is the purpose of the TEMPO group in a forecast?

To describe frequent changes in visibility Signup and view all the answers

What is the reportable value for a visibility of 4600 meters?

4400 Signup and view all the answers

When is variable visibility described in a forecast?

Never Signup and view all the answers

What is the reportable value for a visibility of 9100 meters?

9999 Signup and view all the answers

What is the purpose of the visibility (VVVV) group in a forecast?

To describe visibility in meters Signup and view all the answers

What is the purpose of the icing group in forecasting?

To forecast icing not associated with thunderstorms Signup and view all the answers

How is the type of icing encoded when forecasting more than one type of icing within the same layer?

The highest code figure is used Signup and view all the answers

What is the unit of measurement for the height of the base of the forecasted icing layer?

Hundreds of feet AGL Signup and view all the answers

What is the purpose of the turbulence group in forecasting?

To forecast turbulence not associated with a thunderstorm Signup and view all the answers

What category of aircraft is the turbulence forecast applicable to?

Category II Signup and view all the answers

What happens when forecasting a layer to be thicker than 9,000 feet?

The layer is repeated with the base of the second group coinciding with the top layer given by the first group Signup and view all the answers

What is the format of the turbulence group?

5BhBhBhBtL Signup and view all the answers

What is the purpose of repeating the icing group when forecasting multiple icing layers?

To indicate multiple layers of icing Signup and view all the answers

What is the format of the Non-Convective Low-Level Wind Shear Group in the TAF?

WShxhxhx/dddfffKT Signup and view all the answers

What is the unit of measurement for the wind speed in the Non-Convective Low-Level Wind Shear Group?

Knots Signup and view all the answers

At what height is the wind direction forecasted in the Non-Convective Low-Level Wind Shear Group?

Above the indicated height Signup and view all the answers

What is the purpose of the Non-Convective Low-Level Wind Shear Group in the TAF?

To forecast wind direction and speed above the indicated height Signup and view all the answers

In which part of the TAF does the Non-Convective Low-Level Wind Shear Group appear?

After the cloud forecast and before the altimeter setting forecast Signup and view all the answers

What is the indicator for the wind speed in the Non-Convective Low-Level Wind Shear Group?

KT Signup and view all the answers

What happens to the Non-Convective Low-Level Wind Shear Group once it is included in the forecast?

It remains the prevailing condition until the next FM or BECMG group Signup and view all the answers

When are forecasts for non-convective low-level wind shear not included in the TAF?

When they are expected to occur in the TEMPO groups Signup and view all the answers

What is the purpose of including the cumulonimbus (CB) contraction in the cloud or obscuration group?

To indicate a significant weather condition Signup and view all the answers

What is the time period for which the initial conditions are valid in the TAF example?

From 011600Z to 2144Z Signup and view all the answers

What is the lowest altimeter setting between 011600Z and 012144Z in the TAF example?

30.01 inches of mercury Signup and view all the answers

What is the sky cover condition indicated by the 'FEW' abbreviation in the TAF example?

A surface-based partial obscuration or a layer at or lower than 50 feet Signup and view all the answers

What is the wind direction and speed indicated in the initial conditions of the TAF example?

Winds from 030 degrees at 8 knots Signup and view all the answers

What is the purpose of the 'BECMG' group in the TAF example?

To indicate a change in weather conditions Signup and view all the answers

What is the cloud cover indicated by the 'BKN' abbreviation in the TAF example?

A broken ceiling at 500 feet Signup and view all the answers

What is the time period for which the TEMPO group is valid in the TAF example?

From 011800Z to 012100Z Signup and view all the answers

What is the purpose of the Volcanic Ash (VA) group in the TAF?

To encode all VA plume forecasts provided by the VAAC Signup and view all the answers

What is the unit of measurement for the height of the base of the volcanic ash layer encoded in the VA group?

Hundreds of feet AGL Signup and view all the answers

When forecasting VA to be surface-based, what should be encoded in the TAF?

VA as both present weather and add a VA group Signup and view all the answers

What is the primary source of VA plume forecasts if the responsible VAAC cannot produce them?

Air Force forecasts Signup and view all the answers

What is the format for encoding non-convective low-level wind shear forecasts?

WShxhxhx/dddfffKT Signup and view all the answers

What is the indicator for the Low-level wind shear group?

WS Signup and view all the answers

What is the height of the top of the volcanic ash layer encoded in?

Hundreds of feet AGL Signup and view all the answers

What is the purpose of the Non-Convective Low-Level Wind Shear Group (WShxhxhx/dddfffKT)?

To forecast wind shear not associated with convective activity Signup and view all the answers

When is a temporary condition considered to be predominant in the TEMPO group?

When it lasts more than 30 consecutive minutes or covers more than half of the period Signup and view all the answers

What happens to forecast conditions preceding the FMYYGGgg group?

They are superseded by the conditions forecasted in this group Signup and view all the answers

What is the purpose of the four-digit time resolution in the FMYYGGgg group?

To provide a higher time resolution when necessary Signup and view all the answers

What is the exception to the 30-minute rule in the TEMPO group?

Thunderstorms Signup and view all the answers

When is a four-digit time in whole hours still acceptable in the FMYYGGgg group?

When a forecast and amending events do not require a higher time resolution Signup and view all the answers

What happens when the conditions in the TEMPO group last more than half of the period?

They are considered predominant Signup and view all the answers

What is the purpose of the YY and GG indicators in the TEMPO group?

To indicate the date and time of the forecast Signup and view all the answers

What is the effect of the FMYYGGgg group on the forecast?

It supersedes all preceding forecast conditions Signup and view all the answers

What is the purpose of issuing an amendment (AMD) in a TAF?

To include only the remaining valid period of the TAF Signup and view all the answers

What is the purpose of the four-letter location identifier (CCCC) in a TAF?

To identify the location of the aerodrome Signup and view all the answers

What happens when a correction (COR) is issued in a TAF?

The entire original text of the TAF is reissued with corrections Signup and view all the answers

What is the format of the issue date and time in a TAF?

YYGGggZ Signup and view all the answers

What is the purpose of the valid period (YYG1G1/YYG2G2) in a TAF?

To specify the duration of the forecast Signup and view all the answers

What is the minimum duration of a forecast period in a TAF?

30 hours Signup and view all the answers

What happens when a TAF is amended and the original forecast is no longer valid?

Only the remaining valid period of the TAF is included Signup and view all the answers

What is the wind direction and speed at the beginning of the forecast period in Figure 1.4?

280 degrees at 12 knots gusting to 25 knots Signup and view all the answers

What is the purpose of the message identifier (TAF) in a TAF?

To identify the forecast as a TAF Signup and view all the answers

What is the lowest altimeter setting from 011600Z to 011900Z in Figure 1.4?

29.60 inches of mercury Signup and view all the answers

What is the minimum visibility required to report a weather and/or obscuration?

9,999 meters Signup and view all the answers

What is the purpose of the TEMPO group in weather forecasts?

To describe frequently alternating visibility conditions Signup and view all the answers

What is the forecast maximum temperature at 012000Z in Figure 1.4?

15°C Signup and view all the answers

What is the reportable value for a visibility of 3,500 meters?

3,600 meters Signup and view all the answers

What is the purpose of including Volcanic Ash (VA) in the weather forecast?

To focus the attention of the pilot on existing or expected problems Signup and view all the answers

What is the sky cover at 1500 feet at the beginning of the forecast period in Figure 1.4?

Scattered Signup and view all the answers

What is the substitution for 4,800 meters in OCONUS locations?

5,000 meters Signup and view all the answers

What is the forecast minimum temperature at 021100Z in Figure 1.4?

4°C Signup and view all the answers

What is the unit of measurement for visibility in the table?

Meters Signup and view all the answers

What is the reportable value for a visibility of 1,750 meters?

1,600 meters Signup and view all the answers

What is the visibility at the beginning of the forecast period in Figure 1.4?

8000 meters Signup and view all the answers

What is the wind direction and speed between 011800Z and 011900Z in Figure 1.4?

270 degrees at 12 knots Signup and view all the answers

What is the purpose of including weather and/or obscuration in a forecast when visibility is less than 9,999 meters?

To provide additional information about the weather conditions Signup and view all the answers

What is the significance of the value 9,999 meters in weather forecasts?

It is the threshold for reporting weather and/or obscuration Signup and view all the answers

When is a Forecast Volcanic Ash (VA) reported in the weather forecast?

When VA is observed and the Volcanic Ash Advisory Center (VAAC) forecast includes a surfaced-based VA plume. Signup and view all the answers

What is the correct sequence of cloud groups in the Cloud and Obscuration Group (NsNsNshshshsCC)?

Lowest base first, then increasing Signup and view all the answers

What is the purpose of the summation principle in the Cloud Amount (NsNsNs)?

To determine the total cloud cover Signup and view all the answers

What is the unit of measurement for the height of the base of the cloud layer (mass) in the Cloud Amount (NsNsNs)?

Hundreds of feet Signup and view all the answers

What is the definition of a ceiling in the Cloud and Obscuration Group (NsNsNshshshsCC)?

The height above the earth's surface of the lowest layer reported as broken or overcast Signup and view all the answers

What is the encoding for a totally obscured sky in the Cloud and Obscuration Group (NsNsNshshshsCC)?

VVhshshs Signup and view all the answers

What is the minimum wind speed required to report a Squall (SQ) in a weather forecast?

22 knots Signup and view all the answers

What is the correct encoding for forecast weather in the vicinity?

VCSH Signup and view all the answers

What is the primary purpose of the Air Force Terminal Aerodrome Forecast (TAF) code?

To support AF, Army or DoD wide operations Signup and view all the answers

What is the radius of the area in which forecast elements in the main body of the forecast text apply?

5 statute mile radius of the aerodrome Signup and view all the answers

What is the format of the TAF code derived from?

World Meteorological Organization (WMO) standards Signup and view all the answers

What happens when forecasting weather phenomena outside of the 5 statute mile radius of the aerodrome?

It is encoded as VC (in the vicinity) Signup and view all the answers

What is the purpose of the VC encoding in the TAF code?

To specify weather conditions outside of the 5 statute mile radius of the aerodrome Signup and view all the answers

What is the main difference between the TAF code and the METAR code?

TAF code is used for forecasting weather, while METAR code is used for reporting weather Signup and view all the answers

Why are forecast elements limited to a 5 statute mile radius of the aerodrome?

To ensure safety of aviation Signup and view all the answers

What is the purpose of the TAF encoding?

To provide a concise and accurate representation of weather conditions Signup and view all the answers

What happens to the temporary condition in the TEMPO group when the forecast lasts more than 30 consecutive minutes or is expected to last more than half of the period?

It will be considered predominant and entered in the initial forecast period. Signup and view all the answers

What is the purpose of the YYGGgg format in the FMYYGGgg group?

To indicate the beginning of a self-contained part of the forecast. Signup and view all the answers

What is the maximum duration for a condition to be considered temporary in the TEMPO group?

Less than 30 consecutive minutes. Signup and view all the answers

When can a four-digit time in whole hours be used in the FMYYGGgg group?

Only when a higher time resolution is not required. Signup and view all the answers

What happens to forecast conditions preceding the FMYYGGgg group?

They are superseded by the conditions forecasted in this group. Signup and view all the answers

Why is an exception made for thunderstorms in the TEMPO group?

To allow for 15 minutes of observation time after the storm has passed. Signup and view all the answers

What is the purpose of the TEMPO group in the TAF code?

To indicate temporary conditions that are expected to last less than 30 minutes. Signup and view all the answers

What happens when forecast conditions in the TEMPO group last more than 30 consecutive minutes or are expected to last more than half of the period?

The temporary condition is considered predominant and entered in the initial forecast period. Signup and view all the answers

What is the purpose of the BECMG group in a weather forecast?

To indicate a change to forecast prevailing conditions expected to occur at an unspecified time Signup and view all the answers

What is the duration of the time period described by a BECMG group?

Up to 2 hours Signup and view all the answers

What is the format of the BECMG group in a weather forecast?

BECMG YYGG/YYGeGe Signup and view all the answers

What occurs when the conditions in the BECMG group last more than 30 minutes?

The conditions are reported as predominant Signup and view all the answers

What is the purpose of repeating the entire element(s) when using the BECMG group?

To indicate a change in one or more elements Signup and view all the answers

What is the difference between the BECMG and TEMPO groups?

The BECMG group is used for permanent changes, while the TEMPO group is used for temporary fluctuations Signup and view all the answers

What happens to the forecast conditions after the ending time of the BECMG group?

The forecast conditions are reported as predominant Signup and view all the answers

What is the significance of the YYGeGe group in the BECMG format?

It indicates the end time of the change Signup and view all the answers

What does the abbreviation 'VC' represent in the weather forecast?

Vicinity Signup and view all the answers

Which of the following weather phenomena is NOT considered a type of precipitation?

BR Mist Signup and view all the answers

What is the correct encoding for forecast weather in the vicinity of the aerodrome?

VC Signup and view all the answers

What does the 'FZ' encoding represent in the weather forecast?

Freezing (Super-cooled) Signup and view all the answers

Which of the following weather phenomena is characterized by a well-developed condition in the case of tornadoes or waterspouts?

<ul> <li>Heavy</li> </ul> Signup and view all the answers

What is the purpose of the 'PO' encoding in the weather forecast?

To indicate Well-developed Fog Signup and view all the answers

Which of the following weather phenomena is NOT considered a type of obscuration?

RA Rain Signup and view all the answers

What is the correct encoding for forecast weather with snow grains?

SG Signup and view all the answers

What is the correct format for encoding non-convective low-level wind shear forecasts?

WShxhxhx/dddfffKT Signup and view all the answers

What is the purpose of the Non-Convective Low-Level Wind Shear Group (WShxhxhx/dddfffKT)?

To forecast wind direction and speed above the indicated height Signup and view all the answers

When is a non-convective low-level wind shear forecast included in the TAF?

When expected, following the cloud forecast and before the altimeter setting forecast Signup and view all the answers

What is the unit of measurement for the wind speed in the non-convective low-level wind shear forecast?

Knots Signup and view all the answers

Where is the non-convective low-level wind shear forecast placed in the TAF?

After the cloud forecast and before the altimeter setting forecast Signup and view all the answers

What is the height of the wind shear forecast in the example TAF?

1,500 feet Signup and view all the answers

What is the direction of the wind in the non-convective low-level wind shear forecast in the example TAF?

120 degrees Signup and view all the answers

What is the speed of the wind in the non-convective low-level wind shear forecast in the example TAF?

38 knots Signup and view all the answers

What is the correct forecasting practice for visibility less than 9999 meters?

Report weather and/or obscuration (w'w') Signup and view all the answers

What is the significance of a visibility of 9999 meters in a forecast?

Precipitation is occurring, but not restricting visibility Signup and view all the answers

What is the correct way to report a visibility of 4,800 meters at an OCONUS location?

Report 5000 meters Signup and view all the answers

How should visibility be reported when it alternates frequently from one significant value to another?

Describe the situation with a TEMPO group Signup and view all the answers

What is the purpose of Table 1.1?

To provide a list of reportable visibility values Signup and view all the answers

What should be done with weather such as precipitation when it is not restricting visibility?

Report weather and visibility separately Signup and view all the answers

What is the significance of a visibility of 9999 meters?

Visibility is greater than or equal to 9999 meters Signup and view all the answers

When should weather and/or obscuration (w'w') be reported?

Only when visibility is less than 9999 meters Signup and view all the answers

What happens when forecast conditions in the TEMPO group last more than half of the period indicated by the time YYGG to YYGeGe?

The temporary condition will be considered predominant and entered in the initial forecast period. Signup and view all the answers

What is the purpose of the FMYYGGgg group in the forecast?

To indicate the beginning of a self-contained part of the forecast. Signup and view all the answers

What happens to forecast conditions preceding the FMYYGGgg group?

They are superseded by the conditions forecasted in the FMYYGGgg group. Signup and view all the answers

When is a four-digit time in whole hours (e.g., 1600) still acceptable?

When the forecast and amending events require a higher time resolution. Signup and view all the answers

What is the minimum duration for a condition to be considered in the TEMPO group?

30 consecutive minutes. Signup and view all the answers

What happens when the conditions in the TEMPO group last more than 30 consecutive minutes?

The temporary condition will be considered predominant and entered in the initial forecast period. Signup and view all the answers

What is the purpose of the exception for thunderstorms in the TEMPO group?

To provide an extra 15 minutes for thunderstorms to dissipate. Signup and view all the answers

When is the four-digit resolution used in the FMYYGGgg group?

When the forecast and amending events require a higher time resolution. Signup and view all the answers

What is the primary purpose of the Forecast Volcanic Ash (VA) in the weather forecast?

To report surface-based VA plume Signup and view all the answers

What is the correct encoding for a cloud layer with a base at 1000 feet and covering 5/8ths of the sky?

BKN100 Signup and view all the answers

When forecasting more than one type of icing within the same layer, what should be encoded?

The highest code figure Signup and view all the answers

What is the minimum wind speed required to report a Squall (SQ) in a weather forecast?

16 knots Signup and view all the answers

What is the purpose of the summation principle in the Cloud Amount (NsNsNs)?

To determine the total cloud cover at each level Signup and view all the answers

What category of aircraft is the turbulence forecast applicable to?

Category II (CAT II) Signup and view all the answers

What is the encoding for a totally obscured sky with a vertical visibility of 200 feet?

VV020 Signup and view all the answers

What happens when forecasting a layer to be thicker than 9,000 feet?

The layer is repeated with the base of the second layer coinciding with the top of the first layer Signup and view all the answers

What is the format of the turbulence group?

5BhBhBhBtL Signup and view all the answers

How are the cloud groups arranged in the Cloud and Obscuration Group (NsNsNshshshsCC)?

In ascending order of cloud bases Signup and view all the answers

What is the unit of measurement for the height of the base of the forecasted icing layer?

Hundreds of feet AGL Signup and view all the answers

What is the definition of a ceiling in the Cloud and Obscuration Group (NsNsNshshshsCC)?

The height above the earth's surface of the lowest layer reported as broken or overcast Signup and view all the answers

What is the unit of measurement for the height of the base of the cloud layer (mass) in the Cloud Amount (NsNsNs)?

Hundred of feet Signup and view all the answers

What is the primary purpose of the icing group in forecasting?

To forecast icing not associated with thunderstorms Signup and view all the answers

What is the primary purpose of the turbulence group in forecasting?

To forecast turbulence not associated with thunderstorms Signup and view all the answers

What is the unit of measurement for the icing layer thickness?

Thousands of feet Signup and view all the answers

What is the unit of measurement for the wind speed in the non-convective low-level wind shear forecast group?

Knots Signup and view all the answers

What is the purpose of the non-convective low-level wind shear forecast group?

To forecast wind speed and direction above the indicated height in non-convective weather Signup and view all the answers

What is the format of the non-convective low-level wind shear forecast group?

WSdddfffKT Signup and view all the answers

What is the indicator for the wind speed in the non-convective low-level wind shear forecast group?

KT Signup and view all the answers

What is the purpose of the FMYYGGgg group in the TAF?

To indicate a change in weather conditions Signup and view all the answers

What is the purpose of the BECMG group in the TAF?

To indicate a gradual change in weather conditions Signup and view all the answers

What is the sequence of elements in the TAF?

Cloud forecast, altimeter setting forecast, wind shear forecast Signup and view all the answers

What is the purpose of the WS015/12038KT encoding in the TAF?

To forecast wind speed and direction at 1,500 feet Signup and view all the answers

What is the primary purpose of the Air Force Terminal Aerodrome Forecast (TAF) code?

To forecast weather and solar operations in support of AF, Army or DoD wide operations. Signup and view all the answers

What is the format of the TAF code derived from?

International standards established by the World Meteorological Organization (WMO). Signup and view all the answers

What is the radius of the area in which forecast elements in the main body of the forecast text apply?

5 statute miles Signup and view all the answers

What happens to forecast elements outside of the “vicinity” in forecasts?

They are not specified in the forecast. Signup and view all the answers

What is the purpose of the VC encoding in the TAF code?

To specify weather greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center. Signup and view all the answers

What is the reason for limiting forecast elements to a 5 statute mile radius of the aerodrome?

To ensure safety of aviation through international policy compliance. Signup and view all the answers

What is the format of the TAF code format used for encoding TAFs?

Figure 1.1 Signup and view all the answers

Who establishes the international standards for the TAF code format?

The World Meteorological Organization (WMO) Signup and view all the answers

What is the purpose of the Message Heading (TAF [AMD or COR] CCCC YYGGggZ YYG1G1/YYG2G2)?

To specify the type of forecast being issued Signup and view all the answers

When issuing a correction (COR), what is the procedure?

Issue the entire original text of the TAF, changing only the erroneous elements Signup and view all the answers

What is the purpose of the Four Letter Location Identifier (CCCC)?

To identify the location of the aerodrome Signup and view all the answers

What is the format of the Issue Date and Time (YYGGggZ)?

Current day of the month (YY) and Coordinated Universal Time (UTC) in hours and minutes (GG) followed by the letter Z Signup and view all the answers

What is the purpose of the Valid Period (YYG1G1/YYG2G2)?

To specify the validity period of the TAF Signup and view all the answers

When issuing an amendment (AMD), what is the procedure?

Issue only the remaining valid period of the TAF Signup and view all the answers

What is the purpose of the Forecast Modifier (AMD or COR)?

To indicate whether the TAF is an amendment or correction Signup and view all the answers

What is the purpose of the 30-hour forecast period for TAFs?

To make all TAFs valid for a 30-hour forecast period Signup and view all the answers

What is the format of the valid period in a TAF forecasts, except for amended TAFs?

YYGG/YYGG Signup and view all the answers

What is the purpose of the FM change group in a TAF forecast?

To include all encoded elements in a forecast Signup and view all the answers

What is the rule for indicating valid times in a TAF forecast that starts or stops at midnight UTC?

Use 00 and 24, respectively, to indicate the appropriate valid times Signup and view all the answers

When encoding predominant forecast weather (w'w') groups, which sequence of elements should be considered?

Intensity, proximity, description, precipitation type, obscuration, or other weather phenomena Signup and view all the answers

What is the format of the TEMPO group in a TAF forecast?

TEMPO YYGG/YYGeGe Signup and view all the answers

What is the maximum number of w'w' groups that can be included in a forecast situation?

Three Signup and view all the answers

What is the purpose of the BECMG change group in a TAF forecast?

To indicate a becoming situation Signup and view all the answers

When applicable, what takes precedence over all other w'w' groups?

Funnel clouds and tornadoes Signup and view all the answers

What should be avoided when constructing TAF forecasts?

Overlapping forecast periods Signup and view all the answers

When encoding VC, where should it be placed in relation to the precipitation, obscuration, or other weather phenomena entry?

Before the precipitation, obscuration, or other weather phenomena entry without a space Signup and view all the answers

What is the correct encoding for forecast weather in the vicinity?

The 'VC' indicator is used to denote forecast weather in the vicinity Signup and view all the answers

What is the purpose of limiting change groups to those that are significant to airfield operations?

To avoid confusion and keep the intent of the forecast simple Signup and view all the answers

When an encoded predominant forecast condition is followed by a change group without a w'w' group, what should be encoded?

NSW (no significant weather) Signup and view all the answers

What is the rule for amending TAF forecasts?

Amended TAFs are valid from the current hour to the ending hour of the original TAF Signup and view all the answers

What is the purpose of limiting the w'w' group to three groups?

To ensure clarity and simplicity in the forecast Signup and view all the answers

What is the correct encoding for thunderstorms without precipitation?

TS Signup and view all the answers

What is the height of the base of the cloud layer forecasted in?

Hundreds of feet AGL Signup and view all the answers

What is the only cloud type included in the aerodrome forecast?

Cumulonimbus Signup and view all the answers

What is the range of height values for reporting cloud layers in hundreds of feet AGL?

Less than 50 feet to 10,000 feet Signup and view all the answers

When forecasting a surface-based partial obscuration, what should be encoded?

FEW, SCT, or BKN, followed by the obscuring phenomena Signup and view all the answers

What is the unit of measurement for the height of the base of the cloud layer?

Feet Signup and view all the answers

When is a surface-based partial obscuration considered as a ceiling?

Never Signup and view all the answers

What is the purpose of the reportable cloud layers in Table 1.3?

To determine the height of the cloud base Signup and view all the answers

What should be included in the sky cover summation computation?

The amount of partial obscuration Signup and view all the answers

What is the consideration sequence when constructing predominant forecast weather (w'w') groups?

Intensity/proximity, precipitation type, description, obscuration, or other weather phenomena Signup and view all the answers

When more than three w'w' groups apply to a situation, what should be done?

Select and encode the three w'w' groups that are most significant to operations Signup and view all the answers

What takes precedence over all other w'w' groups when applicable?

Funnel clouds and tornadoes Signup and view all the answers

When encoding VC, where should it be placed?

Before the precipitation, obscuration, or other weather phenomena entry without a space Signup and view all the answers

What is the correct encoding for forecast weather in the vicinity?

The weather phenomena entry at the end of the w'w' group Signup and view all the answers

When an encoded predominant forecast condition is followed by a change group without a w'w' group, what should be encoded?

NSW (no significant weather) Signup and view all the answers

What is the purpose of limiting the w'w' group to three groups?

To prioritize the most significant weather conditions Signup and view all the answers

What is the correct encoding for thunderstorms without precipitation?

TS without any additional encoding Signup and view all the answers

What is the purpose of including a VA group in the TAF?

To encode all VA plume forecasts provided by the VAAC Signup and view all the answers

What is the unit of measurement for the height of the base of the volcanic ash layer?

Hundreds of feet AGL Signup and view all the answers

What is the primary source of VA plume forecasts if the responsible VAAC cannot produce them?

Air Force forecasts Signup and view all the answers

What is the format for encoding non-convective low-level wind shear forecasts?

WS/hxhxhx/dddfffKT Signup and view all the answers

When forecasting VA to be surface-based, what should be encoded in the TAF?

The VA group and the w'w' group Signup and view all the answers

What is the purpose of the Non-Convective Low-Level Wind Shear Group?

To forecast wind shear not associated with convective activity Signup and view all the answers

What is the height of the top of the volcanic ash layer encoded in?

Hundreds of feet AGL Signup and view all the answers

What is the rule for encoding the height of the base of the volcanic ash layer?

Encoded in hundreds of feet AGL Signup and view all the answers

What is the primary purpose of the Air Force Terminal Aerodrome Forecast (TAF) code?

To support AF, Army, or DoD-wide operations Signup and view all the answers

What is the purpose of the icing group in forecasting?

To forecast icing not associated with thunderstorms Signup and view all the answers

What is the radius of the area in which forecast elements in the main body of the forecast text apply?

5 statute miles Signup and view all the answers

What is the purpose of the VC encoding in the TAF code?

To specify weather greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center Signup and view all the answers

What is the unit of measurement for the height of the base of the forecasted icing layer?

Hundreds of feet AGL Signup and view all the answers

What happens when forecasting a layer to be thicker than 9,000 feet?

The icing group is repeated so that the base of the layer expressed by the second group coincides with the top layer given by the first group Signup and view all the answers

What is the format of the TAF code derived from?

World Meteorological Organization (WMO) standards Signup and view all the answers

What is the purpose of the TAF encoding?

To provide weather forecasts for aerodrome operations Signup and view all the answers

What category of aircraft is the turbulence forecast applicable to?

Category II Signup and view all the answers

What is the reason for limiting forecast elements to a 5 statute mile radius of the aerodrome?

To ensure safety of aviation Signup and view all the answers

What is the format of the turbulence group?

5BhBhBhBtL Signup and view all the answers

What is the purpose of the turbulence group in forecasting?

To forecast turbulence not associated with a thunderstorm Signup and view all the answers

What is the main difference between the TAF code and the METAR code?

The TAF code is used for aerodrome operations, while the METAR code is used for route forecasts Signup and view all the answers

How is the type of icing encoded when forecasting more than one type of icing within the same layer?

The highest code figure is encoded Signup and view all the answers

What is the role of AF Weather organizations in relation to TAFs?

They specify, amend, and disseminate TAFs Signup and view all the answers

What is the primary purpose of the Air Force Terminal Aerodrome Forecast (TAF) code?

To provide weather forecasts for pilots Signup and view all the answers

What is the unit of measurement for the height of the base of each sky cover layer in the aerodrome forecast?

Hundreds of feet AGL Signup and view all the answers

When forecasting a surface-based partial obscuration, what should be encoded?

A remark with the obscuring phenomena and applicable layer Signup and view all the answers

What is the only cloud type included in the aerodrome forecast?

Cumulonimbus Signup and view all the answers

What happens when two or more significant sky conditions alternate frequently from one to the other?

Describe the situation with a TEMPO group Signup and view all the answers

How is the height of the base of the cloud layer reported when it is less than 50 feet?

Rounded down to 000 feet Signup and view all the answers

What is the purpose of the remark in the surface-based partial obscuration?

To indicate the obscuring phenomena and applicable layer Signup and view all the answers

What is the range of height values for reporting cloud layers in hundreds of feet AGL when it is greater than 5,000 feet but less than 10,000 feet?

To the nearest 500 feet Signup and view all the answers

What is the definition of an indefinite ceiling?

A vertical visibility of less than 8/8ths Signup and view all the answers

What is the range of height values in feet that should be rounded down to 000 feet when forecasting the height of the base of each sky cover layer?

< 50 feet Signup and view all the answers

What is the contraction used to indicate cumulonimbus in the aerodrome forecast?

CB Signup and view all the answers

How should a surface-based partial obscuration be encoded?

As FEW000, SCT000, or BKN000, with a remark Signup and view all the answers

What should be included in the sky cover summation computation when forecasting a surface-based partial obscuration?

The amount of partial obscuration and the applicable layer Signup and view all the answers

What is the purpose of the VA group in the TAF code?

To forecast volcanic ash plumes Signup and view all the answers

What is considered a surface-based total obscuration?

An obscuration that hides the entire celestial dome (8/8ths) Signup and view all the answers

What is the primary source of VA plume forecasts if the responsible VAAC cannot produce them?

Air Force forecasts Signup and view all the answers

What is the purpose of the reportable layers defined in Table 1.3?

To determine the height of the base of each sky cover layer Signup and view all the answers

What is the height encoded in the VA group in hundreds of feet?

Base of the volcanic ash Signup and view all the answers

What should be encoded in the TAF when forecasting VA to be surface-based?

VA as both present weather (w'w') and add a VA group Signup and view all the answers

What should be done when two or more significant sky conditions alternate frequently from one to another?

Describe the situation with a TEMPO group Signup and view all the answers

What is not considered a ceiling?

A surface-based partial obscuration Signup and view all the answers

What is the purpose of the Non-Convective Low-Level Wind Shear Group (WShxhxhx/dddfffKT)?

To forecast wind shear not associated with convective activity Signup and view all the answers

What is the format for encoding non-convective low-level wind shear forecasts?

WShxhxhx/dddfffKT Signup and view all the answers

What is the indicator for the Low-level wind shear group?

WS Signup and view all the answers

What is the height of the top of the volcanic ash layer encoded in?

Hundreds of feet AGL Signup and view all the answers

What determines the order of the elements in the predominant forecast weather (w'w') group?

Intensity, proximity, description, precipitation type, obscuration, and other weather phenomena Signup and view all the answers

What is the maximum number of w'w' groups that can be included in a forecast situation?

Three Signup and view all the answers

When should funnel clouds (FC) and tornadoes (+FC) be forecast?

Only when they are at the station Signup and view all the answers

What is the correct encoding for forecast weather in the vicinity?

VC at the end of the w'w' group Signup and view all the answers

What should be encoded when an encoded predominant forecast condition is followed by a change group without a w'w' group?

NSW Signup and view all the answers

What takes precedence over all other w'w' groups when applicable?

Funnel clouds and tornadoes Signup and view all the answers

When encoding VC, where should it be placed in relation to the precipitation, obscuration, or other weather phenomena entry?

Before the precipitation, obscuration, or other weather phenomena entry without a space Signup and view all the answers

What is the purpose of limiting the w'w' group to three groups?

To prioritize the most significant weather phenomena Signup and view all the answers

What is the purpose of the icing group in forecasting?

To forecast icing not associated with thunderstorms Signup and view all the answers

How is the type of icing encoded when forecasting more than one type of icing within the same layer?

The highest code figure is encoded Signup and view all the answers

What is the unit of measurement for the height of the base of the forecasted icing layer?

Hundreds of feet Signup and view all the answers

What is the purpose of the turbulence group in forecasting?

To forecast turbulence not associated with a thunderstorm Signup and view all the answers

What is the wind direction and speed at the initial conditions of the forecast in Figure 1.4?

280 degrees at 12 knots gusting to 25 knots Signup and view all the answers

What is the lowest altimeter setting from 011900Z to 022200Z?

29.65 inches of mercury Signup and view all the answers

What category of aircraft is the turbulence forecast applicable to?

Category II (CAT II) aircraft Signup and view all the answers

What happens when forecasting a layer to be thicker than 9,000 feet?

The base of the layer is repeated in the second group Signup and view all the answers

What is the forecast maximum temperature at 012000Z?

15°C Signup and view all the answers

What is the purpose of including volcanic ash and wind shear in the forecast?

To focus the attention of the pilot on existing or expected hazardous problems Signup and view all the answers

What is the format of the turbulence group?

5BhBhBhBtL Signup and view all the answers

What is the sky cover at 2000 feet during the initial conditions of the forecast?

Overcast Signup and view all the answers

What is the purpose of repeating the icing group when forecasting multiple icing layers?

To indicate multiple icing layers Signup and view all the answers

What is the visibility during the initial conditions of the forecast?

8000 meters Signup and view all the answers

What is the forecast minimum temperature at 021100Z?

4°C Signup and view all the answers

What is the change in wind direction and speed between 011800Z and 011900Z?

Winds from 280 degrees at 12 knots to 270 degrees at 12 knots Signup and view all the answers

What is the aggregate total of minutes for which a condition can occur to be considered non-predominant?

Less than 30 minutes Signup and view all the answers

What is the purpose of the YYGGgg format in the FMYYGGgg group?

To indicate the beginning of a self-contained part of the forecast Signup and view all the answers

What happens to forecast conditions preceding the FMYYGGgg group?

They are superseded by the conditions forecasted in this group Signup and view all the answers

When can a four-digit time in whole hours (e.g., 1600) still be used?

When the forecast is for a whole hour Signup and view all the answers

What is the exception for thunderstorms in the TEMPO group?

Organizations will allow 45 minutes Signup and view all the answers

What happens when the conditions in the TEMPO group last more than 30 consecutive minutes?

The conditions are considered predominant Signup and view all the answers

What is the format of the time indicator in the FMYYGGgg group?

Two-digit date YY and four-digit time GGgg Signup and view all the answers

Why is the extra 15 minutes allowed for thunderstorms in the TEMPO group?

To provide for the 15-minute period between the time thunder is last heard and the time the thunderstorm is officially ended Signup and view all the answers

What is the reportable value of visibility in meters, if the prevailing visibility is 10,500 meters?

9,999 Signup and view all the answers

What is the weather and/or obscuration included in the forecast when the visibility is less than 9,999 meters?

Always, regardless of precipitation Signup and view all the answers

What is the purpose of the TEMPO group in the forecast?

To describe temporary changes in weather conditions Signup and view all the answers

What is the reportable value of visibility in meters, if the prevailing visibility is 4,200 meters?

4,000 Signup and view all the answers

What is the statute miles equivalent of 4,800 meters?

2 3/4 Signup and view all the answers

What is the visibility in meters, if the prevailing visibility is 1 3/4 statute miles?

2,600 Signup and view all the answers

What is the reportable value of visibility in meters, if the prevailing visibility is 9,500 meters?

9,999 Signup and view all the answers

What is the note for OCONUS locations for the visibility of 4,800 meters?

Substitute 5,000 meters for 4,800 meters Signup and view all the answers

When constructing predominant forecast weather (w'w') groups, what is the correct sequence of elements to consider?

Intensity/proximity, description, precipitation type, obscuration, other weather phenomena Signup and view all the answers

When more than three w'w' groups apply to a situation, what should be done?

Select and encode the three w'w' groups that are most significant to operations Signup and view all the answers

When encoding VC, where should it be placed in relation to the precipitation, obscuration, or other weather phenomena entry?

Before the precipitation, obscuration, or other weather phenomena entry Signup and view all the answers

What takes precedence over all other w'w' groups when applicable?

Funnel clouds and tornadoes Signup and view all the answers

When an encoded predominant forecast condition is followed by a change group without a w'w' group, what should be encoded?

NSW (no significant weather) Signup and view all the answers

What is the maximum number of w'w' groups that can be included in a forecast situation?

3 Signup and view all the answers

What is the correct encoding for forecast weather in the vicinity?

VCSH (vicinity showers) Signup and view all the answers

What is the purpose of limiting the w'w' group to three groups?

To prioritize the most significant weather conditions Signup and view all the answers

Between 011800Z and 012100Z, what is the wind direction and speed?

Wind from 140 degrees at 12 knots gusting to 18 knots Signup and view all the answers

Between 012300Z and 012400Z, what is the sky cover?

Few at the surface and overcast at 400 feet Signup and view all the answers

What is the unit of measurement for wind speed in the non-convective low-level wind shear forecast?

Knots Signup and view all the answers

What is the purpose of the 'KT' indicator in the non-convective low-level wind shear forecast?

Indicates unit of measurement for wind speed Signup and view all the answers

Between 020100Z and 020300Z, what is the visibility?

200 meters with light freezing drizzle and fog Signup and view all the answers

What is the forecast minimum temperature?

minus 01°C at 021200Z Signup and view all the answers

What is the height above which the wind direction and speed are forecasted in the non-convective low-level wind shear forecast?

1,500 feet Signup and view all the answers

Between 011800Z and 012100Z, what is the icing condition?

Light rime icing from 600 to 5600 feet AGL Signup and view all the answers

When is a non-convective low-level wind shear forecast included in the TAF?

When expected, following the cloud forecast and before the altimeter setting forecast Signup and view all the answers

Between 012145Z and 012400Z, what is the lowest altimeter setting?

29.92 inches of mercury Signup and view all the answers

What is the duration of the non-convective low-level wind shear forecast in the example TAF?

From 011600Z to 012130Z Signup and view all the answers

What is the wind direction and speed forecasted in the non-convective low-level wind shear forecast in the example TAF?

From 120 degrees at 38 knots Signup and view all the answers

Between 020100Z and 020300Z, what is the sky condition?

Totally obscured with vertical visibility 100 feet Signup and view all the answers

What is the forecast maximum temperature?

00°C at 012100Z Signup and view all the answers

What is the format for encoding the wind direction in the non-convective low-level wind shear forecast?

In tens of degrees true Signup and view all the answers

Where is the non-convective low-level wind shear forecast included in the TAF?

Following the cloud forecast and before the altimeter setting forecast Signup and view all the answers

What is the correct way to encode a surface-based partial obscuration?

FEW, SCT, or BKN followed by the applicable layer Signup and view all the answers

What is the purpose of including the amount of partial obscuration in the sky cover summation computation?

To provide a more accurate depiction of sky conditions Signup and view all the answers

How is the height of the base of each sky cover layer forecasted?

In hundreds of feet above ground level Signup and view all the answers

What is the only cloud type included in the aerodrome forecast?

Cumulonimbus Signup and view all the answers

What is the purpose of encoding VRB for ddd?

When forecasting a prevailing wind direction is not possible due to air-mass thunderstorm activity Signup and view all the answers

What is the unit of measurement for the height of the base of the cloud layer?

Hundreds of feet Signup and view all the answers

When should gusts be encoded?

When the maximum speed exceeds the mean speed by 10 knots or more Signup and view all the answers

How is wind speed encoded when it is equal to or greater than 100 knots?

Using three digits Signup and view all the answers

How are reportable cloud layers defined?

By the range of height values Signup and view all the answers

What is the purpose of the remark in a surface-based partial obscuration?

To describe the obscuring phenomena and applicable layer Signup and view all the answers

What is the unit indicator for wind speeds in knots?

KT Signup and view all the answers

When forecasting a surface-based partial obscuration, what is not considered a ceiling?

A surface-based partial obscuration Signup and view all the answers

When is a prevailing wind direction forecasted?

Whenever it can be determined Signup and view all the answers

How is wind direction encoded when winds are calm?

As 00000KT Signup and view all the answers

What happens when forecasting a prevailing wind direction is not possible?

Encode VRB for ddd Signup and view all the answers

When is VRBffGfmfmKT encoded?

When wind speeds are more than 6 knots and a direction cannot be determined Signup and view all the answers

What is the primary purpose of the Air Force Terminal Aerodrome Forecast (TAF) code?

To provide weather forecasts for aviation purposes Signup and view all the answers

What is the radius of the area in which forecast elements in the main body of the forecast text apply?

5 statute miles Signup and view all the answers

What is the purpose of the VC encoding in the TAF code?

To encode weather conditions greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center Signup and view all the answers

What is the format of the TAF code derived from?

International standards established by the World Meteorological Organization (WMO) Signup and view all the answers

What is the main difference between the TAF code and the METAR code?

The TAF code is used for forecasting, while the METAR code is used for reporting Signup and view all the answers

What is the purpose of the TAF encoding?

To provide weather forecasts for aviation purposes Signup and view all the answers

What is the format of the TAF code?

Figure 1.1 Signup and view all the answers

What is the reason for limiting forecast elements to a 5 statute mile radius of the aerodrome?

To ensure safety of aviation Signup and view all the answers

What is the correct format for encoding non-convective low-level wind shear forecasts?

WSddd/ffKT Signup and view all the answers

Where is the non-convective low-level wind shear forecast group located in the TAF?

After the cloud forecast and before the altimeter setting forecast Signup and view all the answers

What is the purpose of the non-convective low-level wind shear forecast group?

To forecast wind shear at low levels Signup and view all the answers

What is the primary purpose of the BECMG group in the weather forecast?

To indicate a change to the forecast prevailing conditions at an unspecified time within a period. Signup and view all the answers

What is the unit of measurement for wind speed in the non-convective low-level wind shear forecast group?

Knots Signup and view all the answers

What is the maximum duration of the time period described by the BECMG group?

2 hours Signup and view all the answers

What is the indicator for wind speed in the non-convective low-level wind shear forecast group?

KT Signup and view all the answers

What is the purpose of repeating the entire element(s) when using the BECMG group to forecast a change in one or more elements?

To ensure that the forecast conditions are consistent throughout the period. Signup and view all the answers

What is the height above which wind direction is forecasted in the non-convective low-level wind shear forecast group?

1,500 feet Signup and view all the answers

What happens to the non-convective low-level wind shear forecast group once it is included in the TAF?

It remains in the TAF until the next FM or BECMG group Signup and view all the answers

What is the purpose of including the non-convective low-level wind shear forecast group in the TAF?

To forecast wind speed and direction at low levels Signup and view all the answers

What is the purpose of the YYGG/YYGeGe format in the BECMG group?

To indicate the starting and ending times of the forecast period. Signup and view all the answers

What is the primary difference between the BECMG and TEMPO groups?

The BECMG group is used for permanent changes, while the TEMPO group is used for temporary fluctuations. Signup and view all the answers

What happens to the forecast conditions preceding the BECMG group?

They are replaced by the new forecast conditions. Signup and view all the answers

What is the purpose of the GeGe group in the BECMG format?

To indicate the ending time of the forecast period. Signup and view all the answers

Between 011800Z and 012100Z, what is the sky cover at the surface?

Few Signup and view all the answers

Beginning at 012145Z, what is the visibility?

9999 meters or greater Signup and view all the answers

Between 012300Z and 012400Z, what is the type of icing reported?

Light rime icing Signup and view all the answers

Between 020100Z and 020300Z, what is the sky condition reported?

Totally obscured with vertical visibility 100 feet Signup and view all the answers

What is the forecast maximum temperature?

00°C at 012100Z Signup and view all the answers

Between 011800Z and 012100Z, what is the wind direction?

140 degrees Signup and view all the answers

Between 012300Z and 012400Z, what is the blowing snow-induced surface-based partial obscuration?

1/8 to 2/8 in coverage Signup and view all the answers

What is the lowest altimeter setting from 020000Z until 022200Z?

29.83 inches of mercury Signup and view all the answers

Between 020100Z and 020300Z, what is the visibility?

200 meters Signup and view all the answers

What is the forecast minimum temperature?

-01°C at 021200Z Signup and view all the answers

What is the indicator for the Low-level wind shear group?

WS Signup and view all the answers

In a TAF, where is the non-convective low-level wind shear forecast included?

After the cloud forecast and before the altimeter setting forecast Signup and view all the answers

What is the format for encoding non-convective low-level wind shear forecasts?

WSdddff KT Signup and view all the answers

What happens to the wind shear group once it is included in the forecast?

It remains the prevailing condition until the next FM or BECMG group or until the end of the forecast valid period Signup and view all the answers

What is the unit of measurement for the wind speed in the low-level wind shear forecast?

Knots Signup and view all the answers

Why is the VRB indicator not used in the non-convective low-level wind shear forecast group?

Because it is not a valid indicator for wind direction Signup and view all the answers

What is the purpose of the TAF code?

To provide a brief, standardized aviation weather forecast Signup and view all the answers

What is the radius of the area in which forecast elements in the main body of the forecast text apply?

5 statute miles Signup and view all the answers

What happens when forecasting wind shear more than once in a single TAF?

All wind shear forecasts are included Signup and view all the answers

What is the purpose of the VA group in the TAF?

To encode volcanic ash plume forecasts provided by the VAAC Signup and view all the answers

What is the height of the base of the volcanic ash layer encoded in?

Hundreds of feet AGL Signup and view all the answers

What is the primary source of VA plume forecasts if the responsible VAAC cannot produce them?

Air Force forecasts Signup and view all the answers

When forecasting VA to be surface-based, what should be encoded in the TAF?

Both the VA group and present weather (w'w') Signup and view all the answers

What is the format of the Non-Convective Low-Level Wind Shear Group (WShxhxhx/dddfffKT)?

All of the above Signup and view all the answers

What is the purpose of the Non-Convective Low-Level Wind Shear Group (WShxhxhx/dddfffKT)?

To forecast wind shear not associated with convective activity Signup and view all the answers

What is the height of the top of the volcanic ash layer encoded in?

Hundreds of feet AGL Signup and view all the answers

What takes precedence over all other weather phenomena when forecasting VA?

VA Signup and view all the answers

What is the primary source of VA plume forecasts?

VAAC forecasts Signup and view all the answers

What is the format of encoding the height of the base of the volcanic ash?

Hundreds of feet AGL Signup and view all the answers

When forecasting more than one type of icing within the same layer, what should be encoded?

The highest code figure Signup and view all the answers

What category of aircraft is the turbulence forecast applicable to?

Category II Signup and view all the answers

When forecasting a layer to be thicker than 9,000 feet, what should be done?

Repeat the icing group with the base of the layer coinciding with the top layer given by the first group Signup and view all the answers

What is the format of the turbulence group?

5BhBhBhBtL Signup and view all the answers

What is the unit of measurement for the height of the base of the forecasted icing layer?

Hundreds of feet AGL Signup and view all the answers

What is the primary purpose of the icing group in forecasting?

To forecast icing not associated with thunderstorms Signup and view all the answers

When forecasting more than one type of turbulence within the same layer, what should be encoded?

The highest code figure Signup and view all the answers

What is the unit of measurement for the icing layer thickness?

Thousands of feet Signup and view all the answers

What is the purpose of the turbulence group in forecasting?

To forecast turbulence not associated with thunderstorms Signup and view all the answers

What happens when forecasting a layer to be thicker than the maximum allowed thickness?

The layer is split into two separate layers Signup and view all the answers

What is the purpose of the icing group in forecasting?

To forecast icing not associated with thunderstorms Signup and view all the answers

How is the type of icing encoded when forecasting more than one type of icing within the same layer?

By encoding the highest code figure Signup and view all the answers

What is the unit of measurement for the height of the base of the forecasted icing layer?

Hundreds of feet AGL Signup and view all the answers

What is the purpose of the turbulence group in forecasting?

To forecast turbulence not associated with thunderstorms Signup and view all the answers

What category of aircraft is the turbulence forecast applicable to?

Category II (CAT II) aircraft Signup and view all the answers

What happens when forecasting a layer to be thicker than 9,000 feet?

The layer is repeated so that the base of the layer expressed by the second group coincides with the top layer given by the first group Signup and view all the answers

What is the format of the turbulence group?

5BhBhBhBtL Signup and view all the answers

What is the purpose of omitting the icing group when no icing is forecast?

To eliminate unnecessary information Signup and view all the answers

What is the purpose of repeating the icing group to indicate multiple icing layers?

To indicate multiple icing layers Signup and view all the answers

What is the unit of measurement for the height of the base of the forecasted turbulence layer?

Hundreds of feet AGL Signup and view all the answers

Study Notes

TEMPO Group Conditions

Conditions must occur once during the specified time period, within 30 consecutive minutes or less than 30 minutes of every cardinal hour, and cover less than half of the period.
Exception: Organizations allow 45 minutes for thunderstorms, including the 15-minute period between the last heard thunder and the official end of the thunderstorm.

FMYYGGgg Group

Indicates the beginning of a self-contained part of the forecast.
The conditions preceding this group are superseded by the conditions forecasted in this group.
Format: FMYYGGgg, where YYGGgg is the four-digit date and time.

Weather ('w'w') Group

Constructed by considering intensity/proximity, description, precipitation type, obscuration, and other weather phenomena.
Only one 'w'w' group is normally included, unless one group does not adequately describe the forecast situation.
Limit to three groups when more than one weather or obscuration condition exists.
Select and encode the three most significant 'w'w' groups when more than three apply.

Weather Phenomena

Funnel clouds (FC) and tornadoes (+FC) take precedence over all other 'w'w' groups and are forecast as at the station, not in the vicinity.
VC may be encoded with thunderstorms (TS), showers (SH), fog (FG), blowing snow (BLSN), blowing dust (BLDU), blowing sand (BLSA), well-developed dust/sand whirls (PO), sand storm (SS), and dust storm (DS).

Forecast Volcanic Ash (VA)

Forecast VA as present weather, regardless of restrictions to visibility, when VA is observed or the VAAC forecast includes a surface-based VA plume.

Forecast Squall (SQ)

Forecast SQ when a strong wind is characterized by a sudden onset, with a wind speed increase of at least 16 knots and sustained at 22 knots or more for at least one minute.

Cloud and Obscuration Group (NsNsNshshshsCC)

Report as often as necessary to indicate all forecast cloud layers up to the first overcast layer.
Arrange groups in ascending order of cloud bases AGL.

Cloud Amount (NsNsNs)

Given as sky clear (SKC), few (FEW), scattered (SCT), broken (BKN), or overcast (OVC).
Follow the three-letter abbreviations with the height of the base of the cloud layer (hshshs) without a space.

Ceiling Height (hshshs)

The height above the earth's surface of the lowest layer reported as broken or overcast, or the vertical visibility into an indefinite ceiling.

Volcanic Ash (VA) Group (VAbbbttt)

Include a VA group in the TAF, following the cloud and obscuration group.
Encode all VA plume forecasts provided by the VAAC in TAF coded products.
The VA plume forecast must be horizontally consistent with the official VAAC forecast.

Non-Convective Low-Level Wind Shear Group (WShxhxhx/dddfffKT)

Use this group only to forecast wind shear not associated with convective activity from the surface up to and including 2,000 feet AGL.

Icing Group

Used to forecast icing not associated with thunderstorms.
Format: 6—Icing group indicator, Ic—Type of icing, hihihi—Height of base of forecasted icing layer in hundreds of feet AGL, tL—Icing layer thickness in thousands of feet.

Turbulence Group (5BhBhBhBtL)

Used to forecast turbulence not associated with a thunderstorm.
Turbulence forecasts apply to category II (CAT II) aircraft.
Omit when no turbulence is forecasted.
Format: 5—Turbulence group indicator, B—Type and intensity of turbulence, hBhBhB—Height of base of forecasted turbulence layer in hundreds of feet AGL.

Roles and Responsibilities

The procedures in this manual apply to all AF Weather organizations or associated contractors performing forecasting of weather and solar operations in support of AF, Army, or DoD wide operations.
Compliance with this publication is driven by international policy to ensure safety of aviation.

TAF Code Format

The Terminal Aerodrome Forecast (TAF) code format is derived from international standards established by the World Meteorological Organization (WMO).
The code format is similar to the Aviation Routine Weather Report (METAR) code found in AFMAN 15-111, Surface Weather Observations.

Forecast Elements

Forecast elements in the main body of the forecast text (clouds, weather, wind, etc.) apply to the area at or within a 5 statute mile radius of the center of the aerodrome.
Specified weather greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center is encoded as VC (in the vicinity).

TAF Encoding

The TAF code format consists of the following groups:
- Wind Group (dddffGfmfmKT)
- Visibility Group (VVVV)
- Weather Group (w'w')
- Cloud Group (Cccc)
- Altimeter Setting Group (Qnhhhhh)
- Non-Convective Low-Level Wind Shear Group (WSdddffKT)
- Icing Group (6IchihihitL)
- Turbulence Group (5BhBhBhBtL)

Wind Group

Wind direction (ddd) is forecast to the nearest 10 degrees.
When wind direction varies more than 60 degrees, encode the prevailing direction for ddd and append the limits of variability to remarks.
When winds are calm, encode dddff as 00000KT.
When wind speed is 6 knots or less and a direction cannot be determined, encode dddff as VRBff.

Visibility Group

The visibility group represents the predominant forecast weather (w'w') groups.
Only one w'w' group is normally included unless one group does not adequately describe the forecast situation.
When more than one weather or obscuration condition exists, limit the w'w' group to three groups.

Icing Group

The icing group is used to forecast icing not associated with thunderstorms.
Format icing groups as: 6—Icing group indicator, Ic—Type of icing, hihihi—Height of base of forecasted icing layer, tL—Icing layer thickness.
When forecasting more than one type of icing within the same layer, encode the highest code figure.

Turbulence Group

The turbulence group is used to forecast turbulence not associated with thunderstorms.
Turbulence forecasts apply to category II (CAT II) aircraft.
Format turbulence groups as: 5—Turbulence group indicator, B—Type and intensity of turbulence, hBhBhB—Height of base of forecasted turbulence layer.

TAF Message Structure

A TAF message consists of a message heading, followed by a series of forecast groups, and ends with a remark section.

Message Heading

The message heading consists of:
- TAF (indicates an amendment or correction)
- Forecast modifier (AMD or COR)
- Four-letter location identifier (CCCC)
- Issue date and time (YYGGggZ)
- Valid period (YYG1G1/YYG2G2)

Forecast Modifier

AMD: indicates an amendment, only includes the remaining valid period of the TAF
COR: indicates a correction, issues the entire original text of the TAF, changing only the TAF header and the erroneous elements

Valid Period

Conditions described by the TEMPO group must occur once during the specified time-period indicated by the date YY and time GG to the date YY and time GeGe
Less than 30 consecutive minutes or occur for an aggregate total of less than 30 minutes of every cardinal hour and cover less than half of the period

Forecast Groups

From (FMYYGGgg): indicates the beginning of a self-contained part of the forecast
Becoming (BECMG): indicates a change in the forecast conditions
Temporary (TEMPO): indicates temporary conditions that occur once during the specified time period

Cloud Reporting

Cumulonimbus (CB) is the only cloud type included in the aerodrome forecast
CB is included in the forecast cloud type whenever a thunderstorm is included in the significant weather group

Surface-Based Obscuration

Indefinite ceiling (VVhshshs): vertical visibility measured in feet, into a surface-based total obscuration
Surface-based partial obscuration: encoded as FEW000, SCT000, or BKN000, with the obscuring phenomena and applicable layer included as a remark

Forecasting Prevailing Visibility

Forecast prevailing visibility in meters, rounded down to the nearest reportable value from Table 1.1.
Include weather and/or an obscuration (w'w') whenever visibility is forecast less than 9,999 meters.
If visibility alternates frequently from one significant value to another, describe the situation with a TEMPO group; do not use variable visibility remarks.

Visibility Table (Table 1.1)

Visibility in statute miles and meters
Examples:
- 0 statute miles = 0 meters
- 1/16 statute miles = 100 meters
- 1/8 statute miles = 200 meters
- ...
- 7 and above statute miles = 9,999 meters

TAF (Terminal Aerodrome Forecast)

TAF example using CB contraction:
- TAF CCCC 101555Z 1016/1122 24025G35KT 0800 TSRA BKN035CB OVC080 QNH2978INS
Interpretation:
- Forecast is for a specific location (CCCC) and time period (101555Z to 1016/1122)
- Wind direction and speed (24025G35KT)
- Visibility (0800)
- Weather conditions (TSRA)
- Cloud layers (BKN035CB OVC080)
- Altimeter setting (QNH2978INS)

Example TAF (Figure 1.3)

Interpretation:
- Forecast is for Barksdale AFB (KBAD) and time period (011555Z to 0116/0222)
- Initial conditions:
  - Wind direction and speed (03008KT)
  - Visibility (0800)
  - Sky cover (FEW000 BKN005 BKN012)
  - Altimeter setting (QNH3001INS)
- TEMPO group:
  - Wind direction and speed (14012G18KT)
  - Visibility (3200)
  - Weather conditions (-SHSN BLSN)
  - Cloud layers (FEW000 OVC006)
- ... and so on

Volcanic Ash (VA) Group

Include a VA group in the TAF, following the cloud and obscuration group
Encode all VA plume forecasts provided by the VAAC in TAF coded products
VA plume forecast must be horizontally consistent with the official VAAC forecast
Note: If the responsible VAAC cannot produce the volcanic ash products, then Air Force forecasts are the primary source

Non-Convective Low-Level Wind Shear Group (WShxhxhx/dddfffKT)

Use this group only to forecast wind shear not associated with convective activity from the surface up to and including 2,000 feet AGL
Encode non-convective low-level wind shear forecasts in the following format:
- WS.Low-level wind shear group indicator
- hxhxhx.Forecast height of the wind shear in hundreds of feet AGL
- ddd.Forecast wind direction, in tens of degrees true, above the indicated height
- ff.Forecast wind speed, in knots, of the forecast wind above the indicated height
- KT.Unit indicator for wind speed in knots

Icing Group (6IchihihitL)

Forecast icing group used to forecast icing not associated with thunderstorms
Repeat as necessary to indicate multiple icing layers
Omit when no icing is forecast
Format icing groups as:
- 6—Icing group indicator
- Ic—Type of icing (Table 1.5)
- hihihi—Height of base of forecasted icing layer in hundreds of feet AGL (Table 1.4)
- tL—Icing layer thickness in thousands of feet (Table 1.6)

Turbulence Group (5BhBhBhBtL)

Forecast turbulence group used only to forecast turbulence not associated with a thunderstorm
Turbulence forecasts apply to category II (CAT II) aircraft
Omit when no turbulence is forecasted
Format turbulence groups as:
- 5—Turbulence group indicator
- B—Type and intensity of turbulence (Table 1.7)
- hBhBhB—Height of base of forecasted turbulence layer in hundreds of feet AGL (Table 1.4)
- tL—Turbulence layer thickness in thousands of feet (Table 1.6)

TAF (AMD or COR) Message Format

TAF message consists of: Message Heading, Message Identifier, Forecast Modifier, Four-Letter Location Identifier, Issue Date and Time, Valid Period, and Forecast Groups

Message Heading

Consists of:
- Message Identifier (TAF)
- Forecast Modifier (AMD or COR)
- Four-Letter Location Identifier (CCCC)
- Issue Date and Time (YYGGggZ)
- Valid Period (YYG1G1/YYG2G2)

Forecast Modifier

AMD (Amendment): used to indicate changes to the original TAF, only includes the remaining valid period
COR (Correction): used to correct errors in the original TAF, includes the entire original text with changes

Four-Letter Location Identifier

CCCC: identifies the location of the airport or weather station

Issue Date and Time

YYGGggZ: current day of the month (YY), hour (GG), and minutes (gg) in UTC, followed by the letter Z

Valid Period

Conditions described by the TEMPO group must occur once during the specified time-period indicated by the date YY and time GG to the date YY and time GeGe

Forecast Groups

FMYYGGgg: indicates the beginning of a self-contained part of the forecast, all forecast conditions preceding this group are superseded by the conditions forecasted in this group
Visibility: forecast in meters, rounded down to the nearest reportable value, include weather and/or an obscuration (w'w') whenever visibility is forecast less than 9,999 meters
Cloud and Obscuration Group: report as often as necessary to indicate all forecast cloud layers up to the first overcast layer, arrange groups in ascending order of cloud bases AGL

Weather Forecast

Forecast Volcanic Ash (VA) as present weather regardless of restrictions to visibility when VA is observed or the Volcanic Ash Advisory Center (VAAC) forecast includes a surface-based VA plume
Forecast Squall (SQ) when a strong wind characterized by a sudden onset in which the wind speed increases at least 16 knots and sustained at 22 knots or more for at least one minute

Cloud and Obscuration Group

Cloud Amount (NsNsNs): given as sky clear (SKC), few (FEW), scattered (SCT), broken (BKN), or overcast (OVC)
Ceiling Height (hshshs): the height above the earth's surface of the lowest layer reported as broken or overcast, or the vertical visibility into an indefinite ceiling

Air Force Terminal Aerodrome Forecast (TAF) Code

The procedures in this manual apply to all AF Weather organizations or associated contractors performing forecasting of weather and solar operations in support of AF, Army, or DoD wide operations.
Compliance with this publication is driven by international policy to ensure safety of aviation.
This chapter provides instructions for encoding Terminal Aerodrome Forecasts (TAFs).
Air Force weather organizations specify, amend, and disseminate TAFs in accordance with AFI 15-128, Weather Roles and Responsibilities, and AFMAN 15-129 Volume 1, Air and Space Weather Operations – Characterization.

Code Format

Air Force weather forecast coding practices are derived from international standards established by the World Meteorological Organization (WMO) as published in WMO No. 306, Manual on Codes, Volume I.1, Part A, Section FM 51, Aerodrome Forecast.
These practices align with those of the Aviation Routine Weather Report (METAR) code found in AFMAN 15-111, Surface Weather Observations.

TAF Encoding

TAF code format is used to encode TAFs (Figure 1.1).
The forecast elements represent the expected condition during the forecast period and in the forecast area.
Unless otherwise specified, forecast elements in the main body of the forecast text (clouds, weather, wind, etc.) apply to the area at or within a 5 statute mile radius of the center of the aerodrome.
Specified weather greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center is encoded as VC (in the vicinity).

TAF Groups

Becoming (BECMG) group: indicates a change to forecast prevailing conditions expected to occur at either a regular or irregular rate at an unspecified time within the period defined by a two-digit date (YY), two-digit change beginning time (GG) with a slash separating a two-digit date (YY) and a two-digit ending time (GeGe) in whole hours.
Temporary (TEMPO) group: indicates temporary fluctuations to the forecast meteorological conditions; conditions described by the TEMPO group must occur once during the specified time-period indicated by the date YY and time GG to the date YY and time GeGe, for less than 30 consecutive minutes or occur for an aggregate total of less than 30 minutes of every cardinal hour and cover less than half of the period indicated by the date YY and time GG to the date YY and time GeGe.
From (FMYYGGgg) group: indicates the beginning of a self-contained part of the forecast indicated by the two-digit date YY and four-digit time GGgg; when the group FMYYGGgg is used, all forecast conditions preceding this group are superseded by the conditions forecasted in this group.

Forecast Weather and Obscuration Group (w'w')

Weather (w'w') group code is defined in AFMAN 15-111 (Table 1.2).
QUALIFIER, INTENSITY, DESCRIPTOR, PRECIPITATION, OBSCURATION, and OTHER are the six categories of weather phenomena.

Wind Forecast

Forecast wind direction, in tens of degrees true, above the indicated height.
Forecast wind speed, in knots, of the forecast wind above the indicated height.
KT is the unit indicator for wind speed in knots.

Non-Convective Low-Level Wind Shear Forecasts

Non-convective low-level wind shear forecasts are included in the TAF, when expected, following the cloud forecast and before the altimeter setting forecast in the initial forecast period or in a FM or BECMG group.
Once included in the forecast, the wind shear group remains the prevailing condition until the next FM or BECMG group or until the end of the forecast valid period if there are no subsequent FM or BECMG groups.
Forecasts for non-convective low-level wind shear will not be included in TEMPO groups.

TEMPO Group Conditions

Conditions in the TEMPO group must occur once during the specified time period.
Conditions can occur for less than 30 consecutive minutes or for an aggregate total of less than 30 minutes of every cardinal hour.
Conditions must cover less than half of the period indicated by the date and time.

Exception for Thunderstorms

Organizations allow 45 minutes for thunderstorms, providing an extra 15 minutes for the 15-minute period between the time thunder is last heard and the time the thunderstorm is officially ended.

FMYYGGgg Group

The time indicator YYGGgg is used to indicate the beginning of a self-contained part of the forecast.
The group FMYYGGgg is used to supersede all forecast conditions preceding this group.
Forecast conditions entered on this line are in effect from the specified time to the end of the forecast period.

Visibility Forecast

Forecast prevailing visibility in meters, rounded down to the nearest reportable value from Table 1.1.
Include weather and/or an obscuration (w'w') whenever visibility is forecast less than 9,999 meters.

Table 1.1 - Visibility (VVVV)

Visibility values in statute miles and meters, with corresponding reportable values.

Forecast Volcanic Ash (VA)

Forecast volcanic ash as present weather regardless of restrictions to visibility when VA is observed or the Volcanic Ash Advisory Center (VAAC) forecast includes a surface-based VA plume.

Forecast Squall (SQ)

Forecast squall when a strong wind characterized by a sudden onset in which the wind speed increases at least 16 knots and sustained at 22 knots or more for at least one minute.

Cloud and Obscuration Group (NsNsNshshshsCC)

Report as often as necessary to indicate all forecast cloud layers up to the first overcast layer.
Arrange groups in ascending order of cloud bases AGL (e.g., lowest base first).

Cloud Amount (NsNsNs)

Cloud amount is given as sky clear (SKC = no clouds); few (FEW = trace to 2/8ths); scattered (SCT = 3/8ths to 4/8ths); broken (BKN = 5/8ths to 7/8ths); or overcast (OVC = 8/8ths).

Ceiling Height (hshshs)

Ceiling is the height above the earth's surface of the lowest layer reported as broken or overcast; or the vertical visibility into an indefinite ceiling.

Wind Forecast

Forecast wind direction, in tens of degrees true, above the indicated height.
Forecast wind speed, in knots, of the forecast wind above the indicated height.

Non-convective Low-Level Wind Shear Forecasts

Included in the TAF, when expected, following the cloud forecast and before the altimeter setting forecast in the initial forecast period or in a FM or BECMG group.
Will not be included in TEMPO groups.

Icing Group (6IchihihitL)

Forecast icing group used to forecast icing not associated with thunderstorms.
Repeat as necessary to indicate multiple icing layers.
Omit when no icing is forecast.

Turbulence Group (5BhBhBhBtL)

Forecast turbulence group used only to forecast turbulence not associated with a thunderstorm.
Turbulence forecasts apply to category II (CAT II) aircraft.
Omit when no turbulence is forecasted.

Roles and Responsibilities

The procedures in this manual apply to all AF Weather organizations or associated contractors performing forecasting of weather and solar operations in support of AF, Army, or DoD wide operations.
Compliance items are driven by international policy to ensure safety of aviation.

Code Format

Air Force weather forecast coding practices are derived from international standards established by the World Meteorological Organization (WMO).
The code format aligns with practices of the Aviation Routine Weather Report (METAR) code.

TAF Encoding

TAF code format consists of: MESSAGE HEADING, Forecast elements, Change groups, and Remarks.
MESSAGE HEADING includes:
- Message identifier of TAF
- Forecast modifier indicating an amendment or correction (AMD or COR)
- Four Letter Location identifier (CCCC)
- Issue Date and Time, YYGGggZ
- Valid Period (YYG1G1/YYG2G2)

Specification of Symbolic Letters

Message identifier of TAF: TAF
Forecast modifier:
- AMD: amendment
- COR: correction
Four Letter Location identifier (CCCC): specifies the location of the aerodrome
Issue Date and Time, YYGGggZ: current day of the month (YY) and the Coordinated Universal Time (UTC) in hours (GG) and minutes (gg) followed by the letter Z
Valid Period (YYG1G1/YYG2G2): the 30-hour period of the forecast beginning time (G1G1) and ending time (G2G2) in whole hours, except for amended TAFs

Change Groups (TTTTT)

Use BECMG YYGG/YYGeGe, TEMPO YYGG/YYGeGe, and FM YYGGgg change groups to indicate changes from the predominant forecast condition at some intermediate date and hour time (YYGGgg) or during a specified period between hours (YYGG to YYGeGe).
TEMPO groups may be used to forecast a change in any or all forecast groups and be followed by a description of all the elements for which a change is forecast to occur intermittently from YYGG to YYGeGe.

Weather Groups (w'w')

Constructed by considering Table 1.2, columns one to five in sequence:
- Intensity/proximity
- Description
- Precipitation type
- Obscuration
- Other weather phenomena
Only one w'w' group is normally included unless one group does not adequately describe the forecast situation.
Limit the w'w' group to three groups when more than three w'w' groups apply to a situation.

Cloud and Visibility

Indefinite Ceiling (VVhshshs): the vertical visibility measured in feet, into a surface-based total obscuration, which hides the entire celestial dome (8/8ths).
Surface-Based Partial Obscuration: encoded as FEW000, SCT000, or BKN000 as appropriate to indicate a surface-based partial obscuration.
Height of Cloud Base (hshshs): forecast the height of the base of each sky cover layer in hundreds of feet AGL using the reportable layers defined in Table 1.3.
Cloud Type (CC): the only cloud type included in the aerodrome forecast is cumulonimbus (CB).

Air Force Terminal Aerodrome Forecast (TAF) Code

The procedures in this manual apply to all AF Weather organizations or associated contractors performing forecasting of weather and solar operations in support of AF, Army, or DoD wide operations.
Compliance items for this publication are driven by international policy to ensure safety of aviation.

Code Format

Air Force weather forecast coding practices are derived from international standards established by the World Meteorological Organization (WMO) as published in WMO No. 306, Manual on Codes, Volume I.1, Part A, Section FM 51, Aerodrome Forecast.
Forecast elements in the main body of the forecast text (clouds, weather, wind, etc.) apply to the area at or within a 5 statute mile radius of the center of the aerodrome.
Specified weather greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center is encoded as VC (in the vicinity).

TAF Encoding

TAF code format includes:
- Predominant forecast weather (w’w’) groups
- Clouds, weather, wind, etc. elements
- Variable sky condition
- Height of cloud base (hshshs)
- Cloud type (CC)
- Volcanic ash (VA) group
- Non-convective low-level wind shear group (WShxhxhx/dddfffKT)
- Icing group
- Turbulence group (5BhBhBhBtL)

w’w’ Group

Constructed by considering Table 1.2, columns one to five in sequence
Includes intensity/proximity, description, precipitation type, obscuration, or other weather phenomena
Limited to three groups when more than one weather or obscuration condition exists
When applicable, funnel clouds (FC) and tornadoes (+FC) take precedence over all other w’w’ groups

VC (In the Vicinity)

Used to encode weather greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center
Placed before the precipitation, obscuration, or other weather phenomena entry without a space
Do not encode intensity qualifiers with VC

Change Group

When an encoded predominant forecast condition is followed by a change group (BECMG or FM) without a w’w’ group, encode the change group w’w’ as NSW (no significant weather)

Volcanic Ash (VA) Group

Includes a VA group in the TAF, following the cloud and obscuration group
Encode all VA plume forecasts provided by the VAAC in TAF coded products
VA plume forecast must be horizontally consistent with the official VAAC forecast

Constructing Predominant Forecast Weather Groups

Intensity/proximity, description, precipitation type, obscuration, or other weather phenomena are considered when constructing predominant forecast weather groups.
Only one weather group is normally included unless one group does not adequately describe the forecast situation.
When more than one weather or obscuration condition exists, limit the weather group to three groups.
When more than three weather groups apply, select and encode the three most significant to operations.

Funnel Clouds and Tornadoes

Funnel clouds (FC) and tornadoes (+FC) take precedence over all other weather groups and are forecast as at the station and not in the vicinity.

Encoding Weather in the Vicinity

VC may be encoded in combination with thunderstorms (TS), showers (SH), fog (FG), blowing snow (BLSN), blowing dust (BLDU), blowing sand (BLSA), and well-developed dust/sand whirls (PO).
When encoding, place VC before the precipitation, obscuration, or other weather phenomena entry without a space between the two.

Indefinite Ceiling and Surface-Based Partial Obscuration

Indefinite Ceiling (VVhshshs) is vertical visibility measured in feet into a surface-based total obscuration, which hides the entire celestial dome (8/8ths).
Surface-based partial obscuration is encoded as FEW000, SCT000, or BKN000, and includes the amount of partial obscuration in the sky cover summation computation.

Height of Cloud Base and Cloud Type

Forecast the height of the base of each sky cover layer in hundreds of feet AGL using the reportable layers defined in Table 1.3.
The only cloud type included in the aerodrome forecast is cumulonimbus (CB), which follows cloud or obscuration height (hshsh) without a space.

Operationally Significant/Hazardous Weather Groups

Volcanic ash (VA) and non-convective wind shear are potentially hazardous problems for aircraft.
VA is forecasted in a group, including the height of the base and top of the volcanic ash layer, and is horizontally consistent with the official VAAC forecast.
Non-convective low-level wind shear is forecasted in a group, including the height of the wind shear in hundreds of feet AGL.

Icing and Turbulence Groups

Icing groups are forecasted to indicate icing not associated with thunderstorms, and include the type of icing, height of base of the icing layer, and thickness of the icing layer.
Turbulence groups are forecasted to indicate turbulence not associated with thunderstorms, and include the type and intensity of turbulence, height of base of the turbulence layer, and thickness of the turbulence layer.

Conditions Described by TEMPO Group

Conditions described by the TEMPO group:
Must occur once during the specified time period (YY and time GG to YY and time GeGe)
Last less than 30 consecutive minutes
Aggregate total of less than 30 minutes of every cardinal hour
Cover less than half of the period indicated
Exception for thunderstorms: Allow 45 minutes for thunderstorms, with an additional 15 minutes for the 15-minute period between the time thunder is last heard and the time the thunderstorm is officially ended.

FMYYGGgg Group

The FMYYGGgg group:
Indicates the beginning of a self-contained part of the forecast
Supersedes all forecast conditions preceding this group
Is used to indicate the beginning of a new forecast period
Includes the four-digit time GGgg in whole hours (e.g., 1600) or with minutes (e.g., 1420)

Visibility Forecast

Visibility forecast:
Rounded down to the nearest reportable value from Table 1.1
Includes weather and/or an obscuration (w'w') whenever visibility is forecast less than 9,999 meters
Does not use variable visibility remarks

Weather and Obscuration (w'w') Groups

Weather and obscuration (w'w') groups:
Constructed by considering Table 1.2, columns one to five in sequence
Include intensity/proximity, description, precipitation type, obscuration, and other weather phenomena
Normally limited to one group, but can be up to three groups if necessary
Prioritize the most significant weather and obscuration conditions
Include funnel clouds (FC) and tornadoes (+FC) which take precedence over all other w'w' groups

VICinity (VC) Encoding

VICinity (VC) encoding:
Used in combination with thunderstorms (TS), showers (SH), fog (FG), blowing snow (BLSN), blowing dust (BLDU), blowing sand (BLSA), well-developed dust/sand whirls (PO), sand storm (SS), and dust storm (DS)
Placed before the precipitation, obscuration, or other weather phenomena entry without a space
Does not include intensity qualifiers with VC

Air Force Terminal Aerodrome Forecast (TAF) Code

The procedures in this manual apply to all AF Weather organizations or associated contractors performing forecasting of weather and solar operations in support of AF, Army, or DoD wide operations.

Roles and Responsibilities

Compliance items for this publication are driven by international policy to ensure safety of aviation.
Air Force weather organizations specify, amend, and disseminate TAFs in accordance with AFI 15-128, Weather Roles and Responsibilities and AFMAN 15-129 Volume 1, Air and Space Weather Operations – Characterization.

Code Format

Air Force weather forecast coding practices are derived from international standards established by the World Meteorological Organization (WMO) as published in WMO No. 306, Manual on Codes, Volume I.1, Part A, Section FM 51, Aerodrome Forecast.
The code format aligns with practices of the Aviation Routine Weather Report (METAR) code found in AFMAN 15-111, Surface Weather Observations.

Forecast Elements

Unless otherwise specified, forecast elements in the main body of the forecast text (clouds, weather, wind, etc.) apply to the area at or within a 5 statute mile radius of the center of the aerodrome.
Specified weather greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center is encoded as VC (in the vicinity).
Forecast elements represent the expected condition during the forecast period and in the forecast area.

TAF Encoding

The TAF code format uses the following format: Becoming (BECMG)—The change-indicator group TTTTT YYGG/YYGeGe.
The BECMG group is used to indicate a change to forecast prevailing conditions expected to occur at either a regular or irregular rate at an unspecified time within the period defined by a two-digit date (YY), two-digit change beginning time (GG) with a slash separating a two-digit date (YY) and a two-digit ending time (GeGe) in whole hours.
The time-period described by a BECMG group is usually for one hour but never exceeds two hours.
The forecast conditions encoded after the BECMG YYGG/YYGeGe group are those elements expected to prevail from the ending time of this change group (GeGe) to the ending time of the forecast period (YYG2G2).

Temporary (TEMPO) Group

The TEMPO group is used to indicate temporary fluctuations to the forecast meteorological conditions.
The forecasted conditions must occur in less than 30 minutes from the time specified in the YYGGgg group.

Wind Group (dddffGfmfmKT)

The wind group represents surface wind direction, speed, and gusts, if any.
Wind direction (ddd) is forecast true wind direction (from which wind is blowing) to the nearest 10 degrees.
When winds are calm, encode dddff as 00000KT.
When wind speed is 6 knots or less and a direction cannot be determined, encode dddff as VRBff.

Visibility Group (VVVV)

Consider all layers and obscuring phenomena to be opaque.

Cloud Type (CC)

The only cloud type included in the aerodrome forecast is cumulonimbus (CB); when appropriate, the contraction CB follows cloud or obscuration height (hshsh) without a space.

Height of Cloud Base (hshshs)

Forecast the height of the base of each sky cover layer in hundreds of feet AGL using the reportable layers defined in Table 1.3.

Non-Convective Low-Level Wind Shear Forecasts

Non-convective low-level wind shear forecasts are included in the TAF, when expected, following the cloud forecast and before the altimeter setting forecast in the initial forecast period or in a FM or BECMG group.
Once included in the forecast, the wind shear group remains the prevailing condition until the next FM or BECMG group or until the end of the forecast valid period if there are no subsequent FM or BECMG groups.
Forecasts for non-convective low-level wind shear will not be included in TEMPO groups.

TAF Format and Structure

Valid period consists of current day of the month (YY) and 30-hour period of forecast beginning time (G1G1) and ending time (G2G2) in whole hours, except for amended TAFs
All times are in UTC
For TAF groups starting and stopping at midnight UTC, use 00 and 24, respectively, to indicate the appropriate valid times

Change Groups (TTTTT)

Use BECMG YYGG/YYGeGe, TEMPO YYGG/YYGeGe, and FM YYGGgg change groups to indicate changes from the predominant forecast condition
Change groups indicate changes at some intermediate date and hour time (YYGGgg) or during a specified period between hours (YYGG to YYGeGe)
TEMPO groups forecast a change in any or all forecast groups and are followed by a description of all the elements for which a change is forecast to occur intermittently
FM change groups must include all encoded elements
Limit change groups to those that are significant to airfield operations
Avoid overlapping forecast periods to keep the intent of the forecast simple
Forecasted conditions must occur in less than 30 minutes from the time specified in the YYGGgg group

Wind Group (dddffGfmfmKT)

Surface wind direction, speed, and gusts, if any
Wind direction (ddd) is forecast true wind direction (from which wind is blowing) to the nearest 10 degrees
Wind speed (ff) is mean forecast wind speed in whole knots
Gusts (Gfmfm) are forecast speed or gusts, in whole knots
Encode gusts when the maximum speed exceeds a mean speed by 10 knots or more or when the peak wind speed is forecast to exceed the lull by 10 knots or more
KT is the unit indicator for wind speeds in knots

Visibility Group (VVVV)

Forecast visibility in meters

Forecast Weather and Obscuration Group (w'w')

AFMAN 15-111 defines forecast weather and obscurations for construction of w'w' groups
Table 1.2 shows the weather (w'w') group code, including qualifiers, weather phenomena, intensity, descriptor, precipitation, and obscurations

Example TAF

Figure 1.3 shows an example TAF for Barksdale AFB, LA
The forecast is for Barksdale AFB, LA (KBAD), issued on the first at 1555Z, valid from 011600Z to 022200Z
The initial conditions are for winds from 030 degrees at 8 knots, visibility 800 meters in partial fog, sky cover is few and broken, and the lowest altimeter setting is 30.01 inches of mercury

BECMG (Becoming) Group

The BECMG group is used to indicate a change to forecast prevailing conditions expected to occur at either a regular or irregular rate at an unspecified time within a defined period.
The format is BECMG YYGG/YYGeGe, where YY is the two-digit date, GG is the two-digit change beginning time, and GeGe is the two-digit ending time in whole hours.
The time period described by a BECMG group is usually for one hour but never exceeds two hours.
The forecast conditions encoded after the BECMG group are those expected to prevail from the ending time of the change group to the ending time of the forecast period.
The forecasted conditions must occur less than 30 minutes after the YYGeGe group start time.

TEMPO (Temporary) Group

The TEMPO group is used to indicate temporary fluctuations to the forecast meteorological conditions.
The forecasted conditions must occur in less than 30 minutes from the time specified in the YYGGgg group.

Wind Group

The wind group is used to indicate surface wind direction, speed, and gusts, if any.
Wind direction is forecast to the nearest 10 degrees, and if direction varies more than 60 degrees, the prevailing direction is encoded along with the limits of variability in remarks.
When winds are calm, the wind direction and speed are encoded as 00000KT.
When wind speed is 6 knots or less and a direction cannot be determined, the wind direction is encoded as VRB.

Wind Speed and Gusts

Wind speed is encoded in whole knots, and when the speed is 100 knots or more, three digits are used.
Gusts are encoded when the maximum speed exceeds the mean speed by 10 knots or more, or when the peak wind speed is forecast to exceed the lull by 10 knots or more.
Gusts of 100 knots or more are encoded in three digits.

Visibility Group

The visibility group is used to indicate the forecast visibility.

Forecast Weather and Obscuration Group

The weather group is used to indicate the forecast weather and obscurations.
The group is constructed by considering the intensity, description, precipitation type, obscuration, and other weather phenomena in sequence.
Only one weather group is normally included, unless one group does not adequately describe the forecast situation.
When more than one weather or obscuration condition exists, the weather group is limited to three groups.
When more than three weather groups apply, the three most significant to operations are selected and encoded.

Non-Convective Low-Level Wind Shear Forecasts

Non-convective low-level wind shear forecasts are included in the TAF when expected, following the cloud forecast and before the altimeter setting forecast in the initial forecast period.
Once included, the wind shear group remains the prevailing condition until the next FM or BECMG group or until the end of the forecast valid period.
Forecasts for non-convective low-level wind shear will not be included in TEMPO groups.

Air Force Terminal Aerodrome Forecast (TAF) Code

Applies to all AF Weather organizations or associated contractors performing forecasting of weather and solar operations in support of AF, Army, or DoD-wide operations.
Compliance with international policy ensures safety of aviation.

Code Format

Derived from international standards established by the World Meteorological Organization (WMO) as published in WMO No. 306, Manual on Codes, Volume I.1, Part A, Section FM 51, Aerodrome Forecast.
Aligns with practices of the Aviation Routine Weather Report (METAR) code found in AFMAN 15-111, Surface Weather Observations.

Forecast Elements

Unless otherwise specified, apply to the area at or within a 5 statute mile radius of the center of the aerodrome.
Specified weather greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center is encoded as VC (in the vicinity).
Do not specify elements outside of the “vicinity” in forecasts.

TAF Encoding

Use the format in Figure 1.1 for encoding TAFs.
Becoming (BECMG) group indicates a change to forecast prevailing conditions expected to occur at either a regular or irregular rate at an unspecified time within the period defined by a two-digit date (YY), two-digit change beginning time (GG) with a slash separating a two-digit date (YY) and a two-digit ending time (GeGe) in whole hours.
Temporary (TEMPO) group indicates temporary fluctuations to the forecast meteorological conditions.

Visibility

Forecast prevailing visibility in meters, rounded down to the nearest reportable value from Table 1.1.
Include weather and/or an obscuration (w’w’) whenever visibility is forecast less than 9,999 meters.
If visibility alternates frequently from one significant value to another, describe the situation with a TEMPO group; do not use variable visibility remarks.

Clouds

Indefinite Ceiling (VVhshshs) is the vertical visibility measured in feet, into a surface-based total obscuration, which hides the entire celestial dome (8/8ths).
Surface-Based Partial Obscuration: encode as FEW000, SCT000, or BKN000 as appropriate to indicate a surface-based partial obscuration.
Code as a remark the obscuring phenomena and the applicable layer.
Variable Sky Condition: if two or more significant sky conditions alternate frequently from one to the other, describe the situation with a TEMPO group; do not use variable sky condition remarks.

Height of Cloud Base

Forecast the height of the base of each sky cover layer in hundreds of feet AGL using the reportable layers defined in Table 1.3.

Cloud Type

Cumulonimbus (CB) is the only cloud type included in the aerodrome forecast; when appropriate, the contraction CB follows cloud or obscuration height (hshsh) without a space.

Volcanic Ash (VA) Group

Include a VA group in the TAF, following the cloud and obscuration group.
Encode all VA plume forecasts provided by the VAAC in TAF coded products.
The VA plume forecast must be horizontally consistent with the official VAAC forecast.

Non-Convective Low-Level Wind Shear Group

Use this group only to forecast wind shear not associated with convective activity from the surface up to and including 2,000 feet AGL.
Encode non-convective low-level wind shear forecasts in the following format:
- WS: Low-level wind shear group indicator.
- hxhxhx: Forecast height of the wind shear in hundreds of feet AGL.
- dddfffKT: Forecast wind direction and speed.

Indefinite Ceiling and Obscuration

Indefinite ceiling refers to a vertical visibility of 8/8ths, which hides the entire celestial dome.
When forecasting a surface-based partial obscuration, encode as FEW000, SCT000, or BKN000, and include the obscuring phenomena and layer in the remark.

Variable Sky Condition

If two or more significant sky conditions alternate frequently, describe the situation with a TEMPO group, and do not use variable sky condition remarks.

Height of Cloud Base

Forecast the height of the base of each sky cover layer in hundreds of feet AGL using the reportable layers defined in Table 1.3.
Reportable cloud layers have specific height ranges and increments:
- < 50 feet: round down to 000 feet
- 50-5000 feet: to the nearest 100 feet
- 5000-10,000 feet: to the nearest 500 feet
- > 10,000 feet: to the nearest 1000 feet

Cloud Type

The only cloud type included in the aerodrome forecast is cumulonimbus (CB), which is encoded without a space after the cloud or obscuration height.

Volcanic Ash (VA) Group

Include a VA group in the TAF, following the cloud and obscuration group, to forecast volcanic ash.
Encode the height of the base and top of the volcanic ash layer in hundreds of feet AGL.
When forecasting VA to be surface-based, encode VA as both present weather and add a VA group.

Non-Convective Low-Level Wind Shear Group

This group is used to forecast wind shear not associated with convective activity from the surface up to and including 2,000 feet AGL.
Encode the forecast height of the wind shear, wind direction, and wind speed in the following format: WS/hxhxhx/dddfffKT.

Icing Group

This group is used to forecast icing not associated with thunderstorms.
Format icing groups as: 6/Ic/hihihi/tL, where:
- 6 is the icing group indicator
- Ic is the type of icing (Table 1.5)
- hihihi is the height of the base of the forecasted icing layer in hundreds of feet AGL (Table 1.4)
- tL is the icing layer thickness in thousands of feet (Table 1.6)

Turbulence Group

This group is used to forecast turbulence not associated with a thunderstorm.
Format turbulence groups as: 5/BhBhBhBtL, where:
- 5 is the turbulence group indicator
- B is the type and intensity of turbulence (Table 1.7)
- hBhBhB is the height of the base of the forecasted turbulence layer in hundreds of feet AGL (Table 1.4)
- tL is the turbulence layer thickness in thousands of feet (Table 1.6)

Air Force Terminal Aerodrome Forecast (TAF) Code

Roles and responsibilities of AF Weather organizations or associated contractors include forecasting of weather and solar operations in support of AF, Army, or DoD-wide operations.
Compliance with international policy ensures safety of aviation.

Code Format

Derived from international standards established by the World Meteorological Organization (WMO) as published in WMO No. 306, Manual on Codes, Volume I.1, Part A, Section FM 51, Aerodrome Forecast.
Aligns with practices of the Aviation Routine Weather Report (METAR) code found in AFMAN 15-111, Surface Weather Observations.

Forecast Elements

Apply to the area at or within a 5 statute mile radius of the center of the aerodrome.
Specified weather greater than 5 statute miles but less than or equal to 10 statute miles of the aerodrome center is encoded as VC (in the vicinity).
Do not specify elements outside of the "vicinity" in forecasts.

TAF Encoding

Use the format specified in Figure 1.1 for encoding TAFs.
Make all TAFs valid for a 30-hour forecast period.
Use groups in parentheses only as condition exists or as required.

Message Heading

Consists of:
- Message identifier of TAF
- Forecast modifier indicating an amendment or correction (AMD or COR)
- Four Letter Location identifier (CCCC)
- Issue Date and Time, YYGGggZ
- Valid Period (YYG1G1/YYG2G2)

Forecast Weather and Obscuration Group

AFMAN 15-111 defines forecast weather and obscurations for construction of w'w' groups.
Table 1.2 provides the Weather (w'w') Group Code.
Forecast weather in the vicinity (e.g., VCSH was included in a previous group, and forecasted to end).
Forecast Volcanic Ash (VA) as present weather regardless of restrictions to visibility when VA is observed or the Volcanic Ash Advisory Center (VAAC) forecast includes a surfaced-based VA plume.
Forecast Squall (SQ) when a strong wind characterized by a sudden onset in which the wind speed increases at least 16 knots and sustained at 22 knots or more for at least one minute.

Cloud and Obscuration Group

Report as often as necessary to indicate all forecast cloud layers up to the first overcast layer.
Arrange groups in ascending order of cloud bases AGL (e.g., lowest base first).
Cloud Amount (NsNsNs) is given as:
- Sky clear (SKC = no clouds)
- Few (FEW = trace to 2/8ths)
- Scattered (SCT = 3/8ths to 4/8ths)
- Broken (BKN = 5/8ths to 7/8ths)
- Overcast (OVC = 8/8ths)
Follow the three-letter abbreviations with the height of the base of the cloud layer (mass) hshshs without a space.

Ceiling Height

The height above the earth's surface of the lowest layer reported as broken or overcast; or the vertical visibility into an indefinite ceiling.

Icing Group

Forecast icing group used to forecast icing not associated with thunderstorms.
Format icing groups as:
- 6—Icing group indicator
- Ic—Type of icing (Table 1.5)
- hihihi—Height of base of forecasted icing layer in hundreds of feet AGL (Table 1.4)
- tL—Icing layer thickness in thousands of feet (Table 1.6)

Turbulence Group

Forecast turbulence group used only to forecast turbulence not associated with a thunderstorm.
Turbulence forecasts apply to category II (CAT II) aircraft.
Format turbulence groups as:
- 5—Turbulence group indicator
- B—Type and intensity of turbulence (Table 1.7)
- hBhBhB—Height of base of forecasted turbulence layer in hundreds of feet AGL (Table 1.4)

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This quiz assesses your understanding of the TEMPO group's weather conditions rules, including time periods, aggregate totals, and exceptions.