Air Masses and Weather Patterns

Air Masses

• Air masses move from areas of high pressure to low pressure
• Air masses are deflected in both hemispheres due to the earth's rotation
• Temperature and moisture in an air mass change as air masses move
• Modification of air mass temperatures occur due to the heterogeneous nature of the air mass
• The climate of the eastern Gulf coast is humid and subtropical year-round
• The northern Gulf coast climate consists of a warm marine type and varies from warm to subtropical
• Hot air holds more moisture than cold air
• Air masses that move from Canada have the symbol cPk
• As temperature increases for a given mass, relative humidity decreases
• As air mass temperature decreases, relative humidity increases
• Air temperature varies with altitude above sea level, the season, and distance from the equator
• A source of an air mass labeled mTw is the Gulf of Mexico
• A warm air mass exhibits stability
• Warm air masses are termed "warm" when moving over a surface that is cooler
• Warm air masses have stratiform clouds
• Warm air rises above cool air, cooling as it ascends
• Buys Ballot's Law helps in estimating a storm's center bearing
• When an observer in the Northern Hemisphere experiences a northeast wind, per Buys Ballot's law, the low pressure center is located to the northwest
• According to Buys Ballot's law, a northwest wind in the Northern Hemisphere indicates low pressure to the northeast
• When facing the surface wind in the Northern Hemisphere, the low-pressure center to the left, slightly behind
• Steaming eastward with a dead ahead wind in a North Atlantic extratropical cyclonic storm places the low pressure center to the north
• Steaming west in the North Atlantic with a dead ahead wind in an extratropical cyclonic storm puts the low pressure to the north
• An observer experiencing a northwest wind in the Southern Hemisphere has the low pressure to the south-southwest
• Steaming west with a dead ahead wind in a South Atlantic extratropical cyclonic storm puts the low directly dead ahead

Cloud Formations

• Minimal cloud formations occur when surface and aloft temperatures are equal
• Classification of clouds occurs according to altitude and how they are formed
• Altocumulus clouds are defined as middle clouds
• Number 5 in illustration D039NG represents altocumulus clouds
• Altostratus clouds are uniform, grayish-white sheets covering large parts of the sky and cause most precipitation in temperate latitudes
• Altostratus clouds are dependable indicators of approaching weather systems
• Number 4 in illustration D039NG refers to altostratus clouds
• Vertical development clouds, also known as "atoll" clouds, are often produced over warm islands due to rising air currents
• Cirrocumulus clouds are high, composed of small white flakes or globular masses and often banded together to form a "mackerel sky"
• Cirrocumulus clouds often known as "mackerel sky" are generally associated with fair weather
• Cirrostratus clouds commonly produce a halo around the Sun or Moon
• Thin, whitish, high cirrus clouds known as "mares' tails" form composed primarily of ice crystals
• Number 1 in illustration D039NG represents cirrus clouds
• Seeing "hook" or "comma" shaped cirrus clouds potentially signals rain with an approaching front
• Cumulonimbus clouds, marked by vertical development (often anvil-shaped), form due to vertical air movements
• Cumulonimbus clouds contribute to gusty winds, thunder, rain or hail, and lightning
• Cumulus clouds transitioning to cumulonimbus indicate probable thunderstorm activity
• Tornados or waterspouts can develop from cumulonimbus clouds
• Approaching a tall cumulus cloud on a warm day characterized by hard edges and rain signals an impending wind speed increase
• Cumulus clouds signify fair weather if the sky is clear except for them

Clouds, Fog, and Dew

• Clouds with the prefix "nimbo" are rain clouds and are sheet or layer clouds
• The appearance of nimbostratus clouds signals rain, poor visibility, dropping barometric pressure, and backing wind
• A low, dark stratus cloud associated with continuous, long-lasting precipitation is a nimbostratus cloud
• A low, uniform stratus resembling fog, but not on the ground, often ends in thick fog if a dying wind is present
• Breakers are steep, unstable waves in shallow water where crests move forward quicker than the wave
• A very light breeze (cat's paw) causes ripples on a small area of still water
• Clouds form when warm, humid air rises, cools, and condenses moisture into droplets
• Convection is responsible for heat transfer consisting of ascending and descending air masses with differing temperatures
• Coriolis is the force resulting from the earth's rotation that deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
• Clear skies, calm air, and a surface cooler than the dew point are conditions necessary for dew
• Dew point is reached when the air becomes saturated with water vapor
• The dew point temperature is lower always lower than the air temperature
• The dew point is the temperature at which the air saturates with water vapor and condensation occurs below that temperature
• Freezing salt water spray can happen at an air temperature below 28°F (-2.2°C)
• The troposphere constitutes 3/4 of the atmosphere and is where weather conditions are most active
• In a weather report, visibility measures the distance at which prominent objects are identifiable
• Visibility isn't easily noted from a moving vessel
• Surface circulation is another term for cyclones
• Advection fog is caused by warm moist moving over a colder surface and is common at sea
• When warm moist air blows over a surface colder than its dew point, is cooled, creating advection fog
• fog clears generally when wind speed increases

Fronts

• A boundary between two air masses defines a front
• A weather front exists only when air masses of different temperatures meet
• Expect frontal activity when two colliding air masses have differing temperatures
• Feathery deposits of ice caused by water vapor sublimating directly into crystalline form on below-freezing objects is frost
• "Frost" is not a form of precipitation
• Hail is a type of precipitation that happens in thunderstorms with strong convection
• Thunderstorms with violent convection that causes ice pellets indicates hail
• Wave height is the vertical distance from crest to trough
• An Isotherm is the line on a weather map connecting points of equal temperature

Lifting and Pressure

• Topographic lifting happens when air is mechanically forced upwards by the slope of the terrain it is moved over
• Mamma are visible mound-like protuberances on the bottom of cumulonimbus clouds that indicate potential breeding grounds for waterspouts and tornadoes
• A millibar measures pressure
• Modification refers to the process by which air mass temperature and/or moisture characteristics change
• Standard barometric pressure as 29.92 inches of mercury is 1013.25 millibars
• A decrease in barometric pressure is associated with rising warm air and proximity to a low pressure area and and inward spiraling circulation
• An isobar is a line on a weather chart connecting places with the same barometric pressure
• A barometer that changes rapidly indicates a change in present weather conditions
• An improving weather forecast is given a slow rise in barometric pressure
• Deteriorating weather conditions approaching are described as a slow gradual fall of the barometer
• Sealevel atmospheric pressure is equal to 14.7 pounds per square inch, and 29.92 inches of mercury.
• Barometers that fall gradually suggest that bad weather is imminent
• The most reliable barometer for a safe boat trip is to watch for gradually falling barometric pressure
• Changing atmospheric levels indicates bad changes.
• There pressure can mean a lot of changes to a boat trip.
• Rapid winds in the next 6 hours are key to understanding pressure

Humidity

• Comparing dry and wet bulb temperatures with a psychrometer reveals relative humidity and dew point
• Relative humidity is the ratio of the actual vapor content at the current temperature to the air's vapor holding capability
• Relative humidity measures water vapor compared to maximum amount it can hold at specific temp
• To calculate standard humidity add both temperatures

Storms and wind

• Wind and storm can influence how weather will happen
• Its imprtant to avoid places there are storms
• You can tell if you are in a dangerous spot

Lows Highs and Clouds

• These thing will affect the sky

Isobars Instrument and Temp

• These can help understand the path to safter places

Wind and Rain

• Weather and movement are affteced by it

Tropics and weather

Tropical Storms

Storm Center

Winds and Directions