Earth-Moon-Sun System (Reviewer.pdf)

EARTH-MOON-SUN SYSTEM A. SOLSTICE AND EQUINOX A solstice is an astronomical event that happens twice each year, when the tilt of the Earth's axis is most inclined toward or away from the Sun, causing the Sun's apparent position in the sky to reach its northernmost or southernmost extreme....

EARTH-MOON-SUN SYSTEM A. SOLSTICE AND EQUINOX A solstice is an astronomical event that happens twice each year, when the tilt of the Earth's axis is most inclined toward or away from the Sun, causing the Sun's apparent position in the sky to reach its northernmost or southernmost extreme. The solstices, together with the equinoxes, are connected with the seasons. In some cultures they are considered to start or separate the seasons while in others they fall in the middle. The cause of the seasons is that the Earth's axis of rotation is not perpendicular to its orbital plane of the solar system. As a consequence, for half the year (from around 20 March to 22 September) the northern hemisphere is inclined toward the Sun, with the maximum around 21 June, while for the other half year the southern hemisphere has this distinction, with the maximum around 21 December. The two moments when the inclination of Earth's rotational axis has maximum effect are the solstices. During the northern solstice, places situated at latitude 66.56° north, known as the Arctic Circle will see the Sun just on the horizon during midnight, and all places north of it will see the Sun above horizon for 24 hours. That is the midnight sun or midsummer-night sun or polar day. On the other hand, places at latitude 66.56° south, known as the Antarctic Circle will see the Sun just on the horizon during midday, and all places south of it will not see the Sun above horizon at any time of the day. That is the polar night. During the southern solstice the effects on both hemispheres are just the opposite. At the temperate latitudes, during summer the Sun remains longer and higher above the horizon, while in winter it remains shorter and lower. This is the cause of summer heat and winter cold. An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the Sun being vertically above a point on the Equator. An equinox happens each year at two specific moments in time, when there is a location on the Earth's Equator where the center of the Sun can be observed to be vertically overhead, occurring around March 20/21 and September 22/23 each year. B. TIDES Tides are the rising of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the bathymetry of oceans, seas and estuaries. The moment that the tidal current ceases, is called slack tide. Then the tide reverses direction and is said to be turning. Approximately twice a month, around new moon and full moon when the Sun, Moon, and Earth form a line, the tidal force due to the sun reinforces that due to the Moon. The tide's range is then at its maximum; this is called the spring tide. When the Moon is at first quarter or third quarter, 1 the sun and Moon are separated by 90° when viewed from the Earth, and the solar tidal force partially cancels the Moon's. At these points in the lunar cycle, the tide's range is at its minimum; this is called the neap tide. Tides may be semidiurnal (two high waters and two low waters each day), or diurnal (one tidal cycle per day). In most locations, tides are semidiurnal. Because of the diurnal contribution, there is a difference in height (the daily inequality) between the two high waters on a given day; these are differentiated as the higher high water and the lower high water in tide tables. Similarly, the two low waters each day are referred to as the higher low water and the lower low water. The daily inequality changes with time and is generally small when the Moon is over the equator. C. ECLIPSE An eclipse is an astronomical event that occurs when one celestial object moves into the shadow of another. When an eclipse occurs within a stellar system, such as the solar system, it forms a type of syzygy— the alignment of three or more celestial bodies in the same gravitational system along a straight line. The term eclipse is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth. However, it can also refer to such events beyond the Earth-Moon system: for example, a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its host planet, or a moon passing into the shadow of another moon. A syzygy is the alignment of three or more celestial bodies in the same gravitational system along a straight line. The word is usually used in context with the Sun, Earth, and the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of syzygy, as do transits and occultation there is a syzygy between a star and two celestial bodies, such as a planet and a moon. The shadow cast by the object closest to the star intersects the more distant body, lowering the amount of luminosity reaching the latter's surface. The region of shadow cast by the occulting body is divided into an umbra, where the radiation from the star's radiation-emitting photosphere is completely blocked, aa penumbra, where only a portion of the radiation is blocked, and antumbra, extending beyond the tip of the umbra, within which the Moon is completely in front of the Sun but too small to completely cover it. A total eclipse will occur when the observer is located within the umbra of the occulting object. Totality occurs at the point of maximum phase during a total eclipse, when the occulted object is completely covered. When the star and a smaller occulting object are nearly spherical, the umbra forms a cone-shaped region of shadow in space. Beyond the end of the umbra is a region called the antumbra, where a planet or moon will be seen transiting across the star but not completely covering it. For an observer inside the antumbra of a solar eclipse, for example, the Moon appears smaller than the Sun, resulting in an annular eclipse. The remaining volume of shadowed space, where only a fraction of the occulting object overlaps the star, is called the penumbra. An eclipse that does not reach totality, such as when the observer is in the penumbra, is called a partial eclipse. An occultation of the Sun by the Moon is termed a solar eclipse. The type of solar eclipse event depends on the distance of the Moon from the Earth during the event. A total solar eclipse occurs when the Earth intersects the umbra portion of the Moon's 2 shadow. When the umbra does not reach the surface of the Earth, the Sun is only partially occluded, resulting in an annular eclipse. Partial solar eclipses occur when the viewer is inside the penumbra. During a solar eclipse, the Moon can sometimes perfectly cover the Sun because its apparent size is nearly the same as the Sun when viewed from the Earth. A solar eclipse is actually a misnomer; the phenomenon is more correctly described as an occultation of the Sun by the Moon or an eclipse of the Earth by the Moon. Lunar eclipses occur when the Moon passes through the Earth's shadow. Since this occurs only when the Moon is on the far side of the Earth from the Sun, lunar eclipses only occur when there is a full moon. Unlike a solar eclipse, an eclipse of the Moon can be observed from nearly an entire hemisphere. For this reason it is much more common to observe a lunar eclipse from a given location. A lunar eclipse also lasts longer, taking several hours to complete, with totality itself usually averaging anywhere from about 30 minutes to over an hour. There are three types of lunar eclipses: penumbral, when the Moon crosses only the Earth's penumbra; partial, when the Moon crosses partially into the Earth's umbra; and total, when the Moon circles entirely within the Earth's umbra. Total lunar eclipses pass through all three phases. Even during a total lunar eclipse, however, the Moon is not completely dark. Sunlight refracted through the Earth's atmosphere intersects the umbra and provides a faint illumination. Much as in a sunset, the atmosphere tends to scatter light with shorter wavelengths, so the illumination of the Moon by refracted light has a red hue. FACTORS AFFECTING CLIMATE WEATHER refers to the specific conditions of the atmosphere at a particular place and time. It is measured in terms of such parameters as wind, temperature, humidity, atmospheric pressure, cloudiness and precipitation. In most places, weather can change from hour to hour and season to season. CLIMATE is the average weather and its long term variability over a particular place and time (say a month, a season, a year or several years). SEASON is a division of the year according to some regularly recurrent phenomena, usually astronomical or climatic. In the tropics, precipitation is the primary factor; thus, nearly all regions have their rainy season and dry season. Altitude  As altitude increases, the corresponding temperature of air decreases  It decreases at the environmental lapse rate of 6.4oC/1000m  Solar radiation only turns into heat when it is absorbed by a body of matter  Lower down in the atmosphere the air is denser and contains more water vapor, air molecules, dust etc.  Therefore more energy can be absorbed and turned into heat (longwave radiation) at lower elevations  Heat from the surface of the earth moves up through longwave radiation and convection currents Latitude  Latitude controls the amount of solar radiation that reaches the surface of the earth  As latitude increase the angle at which the sun's rays hit the ground decreases  This effect is amplified by the tilt of the Earth and the resultant seasons  This means that the same amount of energy coming from the sun is spread out over a greater area  This leads to decreased temperatures and evaporation rates at higher latitudes  As the thickness of atmosphere increases the amount of absorption, scattering, and reflection increases leading to a corresponding decrease in light reaching the ground  The differential heating of the land, air, and water produced by these latitudinal variations leads to the creation of global winds and ocean currents 3 Wind  Wind is caused by differences in pressure resulting from differential heating of the earth’s surface  As the air molecules are heated they move more rapidly decreasing the density of an air mass and it rises  Warmer air is also able to hold more water vapor than cold air so it is more moist  Areas of warm rising air have low pressures  Winds result from the earth trying to equalize pressure from areas of high pressure to those with a low pressure across a pressure gradient  An example of this is off and on shore breezes  Theoretically global wind patterns would be two large convection cells with warm air rising at the equator and falling at the poles which in turn would flow back to the equator  However, other forces affect the rising and falling of air on the earth’s surface  The Coriolis Force deflects wind to the right in the northern hemisphere and to the left in the southern hemisphere  Convection cells form where warm air coming from the equator meets cold air moving in the opposite direction creating a high pressure system as the air sinks  These subtropical highs occur at approximately 30o and polar fronts occur at approximately 60o  The descending air of the subtropical highs leads to two wind patterns on the surface, the trade winds (blowing towards the equator) and the westerlies (blowing towards the poles)  The trade winds converge near the equator and rise as they are heated creating the area known as the Inter-Tropical Convergence Zone (ITCZ) or doldrums  The westerlies meet winds coming from the polar fronts which forces air up creating the subpolar lows Humidity  Humidity is the amount of water vapor in the air.  Relative humidity is defined as the ratio of the partial pressure of water vapor in a parcel of air to the saturated vapor pressure of water vapor at a prescribed temperature.  Humidity indicates the likelihood of precipitation, dew, or fog. Precipitation  Precipitation is any product of condensation of atmospheric water vapor that is deposited on the earth’s surface.  It is divided into three categories: whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice.  Liquid forms of precipitation are rain and drizzle. Rain has a water droplet of 0.5 mm or greater in size while drizzle is any droplet of less than 0.5 mm.  Rain or drizzle that freezes on contact within a subfreezing air mass is called "freezing rain" or "freezing drizzle".  Frozen forms of precipitation include snow, ice needles, ice pellets, hail, and graupel. Trade winds are the prevailing pattern of easterly surface winds found in the tropics near the Earth's equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. Prevailing winds are winds that blow predominantly from a single general direction over a particular point on the Earth's surface. Dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface. Fronts are boundaries between air masses of different temperatures. They are actually zones of transition, but sometimes the transition zone, called a frontal zone, can be quite sharp. 4  Four Kinds of Fronts Cold Front is a front in which cold air is replacing warm air at the surface. Some of the characteristics of cold fronts include the following:  The slope of a typical cold front is 1:100 (vertical to horizontal).  Cold fronts tend to move faster than all other types of fronts.  Cold fronts tend to be associated with the most violent weather among all types of fronts.  Cold fronts tend to move the farthest while maintaining their intensity.  Cold fronts tend to be associated with cirrus well ahead of the front, strong thunderstorms along and ahead of the front, and a broad area of clouds immediately behind the front (although fast moving fronts may be mostly clear behind the front).  Cold fronts can be associated with squall lines (a line of strong thunderstorms parallel to and ahead of the front). Weather Prior to the Passing Contact with the After the Passing Phenomenon of the Front Front of the Front Temperature Warm Cooling suddenly Cold and getting colder Atmospheric Pressure Decreasing steadily Leveling off then Increasing steadily increasing Winds South to southeast Variable and gusty West to northwest Precipitation Showers Heavy rain or snow, Showers then clearing hail sometimes Clouds Cirrus and cirrostratus Cumulus and Cumulus changing later to cumulus cumulonimbus and cumulonimbus Warm Front is a front in which warm air replaces cooler air at the surface. Some of the characteristics of warm fronts include the following:  The slope of a typical warm front is 1:200 (more gentle than cold fronts).  Warm fronts tend to move slowly.  Warm fronts are typically less violent than cold fronts.  Although they can trigger thunderstorms, warm fronts are more likely to be associated with large regions of gentle ascent (stratiform clouds and light to moderate continuous rain).  Warm fronts are usually preceded by cirrus first (1000 km ahead), then altostratus or altocumulus (500 km ahead), then stratus and possibly fog.  Behind the warm front, skies are relatively clear (but change gradually).  Warm fronts are associated with a frontal inversion (warm air overrunning cooler air). Weather Phenomenon Prior to the Passing Contact with the After the Passing of the Front Front of the Front Temperature Cool Warming suddenly Warmer then leveling off Atmospheric Pressure Decreasing steadily Leveling off Slight rise followed by a decrease Winds South to southeast Variable South to southwest Precipitation Showers, snow, sleet or Light drizzle None drizzle Clouds Cirrus, cirrostratus, Stratus, sometimes Clearing with scattered altostratus, nimbostratus, cumulonimbus stratus, sometimes and then stratus scattered cumulonimbus 5  Occluded Fronts are fronts that indicate mature storm systems. An occluded front because cold fronts move faster than warm fronts, they can catch up to and overtake their related warm front. Stationary Front is a front that does not or barely moves. They behave like warm fronts but are more quiescent. Intertropical Convergence Zone (ITCZ) is a term that is used to describe the North-East and South-East trade wind convergence. Storm refers to any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather. It may be marked by strong wind, thunder and lightning (a thunderstorm), heavy precipitation, such as ice (ice storm), or wind transporting some substance through the atmosphere (as in a dust storm, snowstorm, hailstorm, etc). Classification of Storms Ice Storm is one of the most dangerous forms of winter weather. When surface temperatures are below freezing, but a thick layer of above freezing air remains aloft above ground level, rain can fall into the freezing layer and freeze upon impact into a "glaze". In general, 8 millimeters (1/4 in) of accumulation is all that is required, especially in combination with breezy conditions, to start downing power lines as well as tree limbs. Ice storms also make unheated road surfaces too slick to drive upon. Ice storms can vary in time range from hours to days and can cripple both small towns and large urban centers alike. Blizzard is accompanied by gale-force winds, heavy snow (accumulating at a rate of at least 5 centimeters (2 in) per hour), and very cold conditions (below approximately -100 Celsius or 140F). Snowstorm is a heavy fall of snow accumulating at a rate of more than 5 centimeters (2 in) per hour that lasts several hours. Snow storms, especially ones with a high liquid equivalent and breezy conditions, can down tree limbs, cut off power, and paralyze travel over a large region. Ocean Storm is a storm condition out at sea having sustained winds of 48 knots (55 mph or 90 km/h) or greater. Usually just referred to as a storm, these systems can sink vessels of all types and sizes. Firestorm is a conflagration which attain such intensity that they create and sustain their own wind systems. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires. Dust devil is a small, localized updraft of rising air. Windstorm is a severe weather condition indicated by high winds and with little or no rain, like European windstorm. Squall is a sudden onset of wind increase of at least 16 knots (30 km/h) or greater sustained for at least one minute. Gale is an extratropical storm with sustained winds between 34-48 knots (39-55 mph or 63–90 km/h). Thunderstorm is a type of storm that generates lightning and the attendant thunder. It is normally accompanied by heavy precipitation. Thunderstorms occur throughout the world, with the highest frequency in tropical rainforest regions where there are conditions of high humidity and temperature along with atmospheric instability. These storms occur when high levels of condensation form in a volume of unstable air that generates deep, rapid, upward motion in the atmosphere. The heat energy creates powerful rising air currents that swirl upwards to the tropopause. Cool descending air currents produce strong downdraughts below the storm. After the storm has spent its energy, the rising currents die away and downdraughts break up the cloud. Individual storm clouds can measure 2–10 km across. Hailstorm is a type of storm that precipitates chunks of ice. Hailstorms usually occur during regular thunder storms. While most of the hail that precipitates from the clouds is fairly small and virtually harmless, there have been cases of hail greater than 2 inches diameter that caused much damage and injuries. 6 Tornado is a violent, destructive wind storm occurring on land. Usually its appearance is that of a dark, funnel-shaped cyclone. Often tornadoes are preceded by a thunderstorm and a wall cloud. Tropical Cyclone is a storm system with a closed circulation around a centre of low pressure, fueled by the heat released when moist air rises and condenses. The name underscores its origin in the tropics and their cyclonic nature. Tropical cyclones are distinguished from other cyclonic storms such as nor'easters and polar lows by the heat mechanism that fuels them, which makes them "warm core" storm systems. Tropical cyclones form in the oceans if the conditions in the area are favorable, and depending on their strength and location, there are various terms by which they are called, such as tropical depression, tropical storm, hurricane and typhoon. Tropical Cyclone-related Concepts Eye and Center. A strong tropical cyclone will harbor an area of sinking air at the center of circulation. If this area is strong enough, it can develop into a large eye. Weather in the eye is normally calm and free of clouds, although the sea may be extremely violent. The eye is normally circular in shape, and may range in size from 3 kilometres (1.9 mi) to 370 kilometres (230 mi) in diameter. Stadium effect. Intense, mature tropical cyclones can sometimes exhibit an outward curving of the eyewall's top, making it resemble a football stadium. Central dense overcast. The central dense overcast is the concentrated area of strong thunderstorm activity near the center of a tropical cyclone. Eyewall. The eyewall is a circle of strong thunderstorms that surrounds the eye; here is where the greatest wind speeds are found, where clouds reach the highest, and precipitation is the heaviest. The heaviest wind damage occurs where a tropical cyclone's eyewall passes over land. Eyewall replacement cycles. Eyewall replacement cycle occurs naturally in intense tropical cyclones. When cyclones reach peak intensity they usually have an eyewall and radius of maximum winds that contract to a very small size, around 10 kilometres (6.2 mi) to 25 kilometres (16 mi). Outer rainbands can organize into an outer ring of thunderstorms that slowly moves inward and robs the inner eyewall of its needed moisture and angular momentum. When the inner eyewall weakens, the tropical cyclone weakens (in other words, the maximum sustained winds weaken and the central pressure rises.) The outer eyewall replaces the inner one completely at the end of the cycle. The storm can be of the same intensity as it was previously or even stronger after the eyewall replacement cycle finishes. The storm may strengthen again as it builds a new outer ring for the next eyewall replacement. Landfall. A landfall is when a storm's center (the center of its circulation, not its edge) crosses the coastline. Tropical depression is an organized system of clouds and thunderstorms with a defined, closed surface circulation and maximum sustained winds of less than 17 metres per second (33 kn) or 39 miles per hour (63 km/h). It has no eye and does not typically have the organization or the spiral shape of more powerful storms. However, it is already a low-pressure system, hence the name "depression". Tropical storm is an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds between 17 metres per second (33 kn) (39 miles per hour (63 km/h)) and 32 metres per second (62 kn) (73 miles per hour (117 km/h)). At this point, the distinctive cyclonic shape starts to develop, although an eye is not usually present. Typhoon is a system with sustained winds of at least 33 metres per second (64 kn) or 74 miles per hour (119 km/h). A cyclone of this intensity tends to develop an eye, an area of relative calm (and lowest atmospheric pressure) at the center of circulation. The eye is often visible in satellite images as a small, circular, cloud-free spot. Surrounding the eye is the eyewall, an area about 16 kilometres (9.9 mi) to 80 kilometres (50 mi) wide in which the strongest thunderstorms and winds circulate around the storm's center. Maximum sustained winds in the strongest tropical cyclones have been estimated at about 85 metres per second (165 kn) or 195 miles per hour (314 km/h). Low Pressure is a region where the atmospheric pressure is lower in relation to the surrounding area. Low pressure systems form under areas of upper level divergence on the east side of upper troughs, or due to localized heating caused by greater insolation or active thunderstorm activity. High Pressure is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment. Winds within high-pressure areas flow outward due to the higher density air near their center and friction with land. 7 Monsoon is a seasonal prevailing wind that lasts for several months, caused by the development of a thermal low over a land mass normally within the subtropics. Northeast Monsoon is locally known as "Amihan". It affects the eastern portions of the country from October up to late March, starts over Siberia as a cold, dry air mass but gathers moisture as it travels across the Pacific Ocean before reaching the eastern sections of the Philippines is characterized by widespread cloudiness with rains and showers. The North Pacific Trades gradually replaces the NE Monsoon in March, appears in all seasons and blows dominantly from March to April, giving strong convective activity. Southwest Monsoon is locally known as "Habagat", it affects the country from July to September, is very warm and humid, occurs when warm moist air flows over the country from the southwest direction, is characterized by heavy rainfall that may last for a week. It brings the rainy season to the western portion of the country. Definition and Description of Weather Forecast Terminologies Used and Adopted by PAGASA A. Cloud Description SKY CONDITION DEFINITION/DESCRIPTION Clear or Sunny Skies State of the sky when it is cloudless, totally clear or with a few small light clouds visible. Has a total cloud cover of less than one okta. Partly Cloudy State of the sky is within 2-5 oktas total cloud cover or has between 30% to 70% cover of the celestial dome. Partly Cloudy to at Times Cloudy Mostly partly cloudy but there are times when more than 70% of the celestial dome is covered with clouds. Mostly or Mainly Cloudy The sky is mostly covered with clouds but with possible brief periods of sunshine. The total cloud cover is between 6 to 8 oktas. Cloudy The sky is covered with clouds between 6 to 8 oktas or has more than 70% cloud cover. Predominantly more clouds than clear sky. For a longer period during the day, the sun is obscured by clouds. Overcast The sky is totally or completely covered with thick and opaque clouds, 8 oktas or around 100% cloud cover. B. Precipitation (Rain and Rainshowers) Description Rain  Overcast sky with continuous or steady precipitation that may last several hours.  Has a water droplets of 0.5 mm or greater in size but if widely scattered the drops may be smaller.  Associated with meso-scale (synoptic) system or macro-scale (large scale) system like TC's, Easterly Waves, Monsoons, Fronts and ITCZ. RAIN CLASSIFICATION DEFINITION/DESCRIPTION Very Light Rains Scattered drops that do not completely wet an exposed surface regardless of duration. Light Rains The rate of fall is from trace to 2.5 mm per hour. Individual drops easily identified and puddles (small muddy pools) form slowly. Small streams may flow in gutters. Moderate Rains The rate of fall is between 2.5 mm to 7.5 mm per hour. Puddles rapidly forming and down pipes flowing freely. Heavy Rains The rate of fall is greater than 7.5 mm per hour. The sky is overcast, there is a continuous precipitation. Falls in sheets, misty spray over hard surfaces. May cause roaring noise on roofs. Monsoon Rains Heavy and continuous precipitation attributed to either the Southwest or Northeast Monsoon. Occasional Rains Not frequent but is recurrent precipitation. Widespread Rains Precipitation occurring extensively throughout an area. Frequent Rains Precipitation occurring regularly and often throughout the time duration. Intermittent Rains Precipitation which ceases at times and re-occur again. 8  Rainshowers  Precipitation of short duration but usually of greater intensity from convective clouds (primarily cumulus or cumulonimbus)  Characterized by sudden start and sudden end of precipitation, rapid change in intensity. RAINSHOWERS DEFINITION/DESCRIPTION Scattered Rainshowers The rain-bearing clouds is distributed spatially resulting to rainshowers occuring to the bigger part of the forecasted area. Isolated Rainshowers The rain-bearing clouds is small and isolated resulting to rainshowers occuring only to a small part of the forecasted area. Occasional Rainshowers There is a large amount of convective clouds and precipitation occurs in most parts of the forecasted area occasionally, and varying in rainfall amount. Squally Rainshowers Showers accompanied by brief but sudden strong or gale force winds. C. Wind Description UNITS in UNITS in WIND DESCRIPTION KPH KNOTS DESCRIPTION AS OBSERVED Light Winds 19 or 10 or less Wind felt on face. less Ordinary wind vanes moved by wind. Leaves rustle. Moderate Winds 20-29 11-16 Wind raises dust and loose paper. Small branches are moved. Moderate to Occasionally Strong Moderate winds mostly persist but there are instances during the forecast period that it reaches strong wind force. Fresh Winds* 30-39 17-21 Small trees in leaf begin to sway. Crested wavelets appear on inland waters. Strong Winds 40-50 22-27 Large branches in motion. Whistling heard in telephone wires. Umbrellas used with difficulty. Gale: 1 Near Gale* 51-62 28-33 Whole trees in motion. Inconvenience felt when walking against wind. Twigs break off road. Cars veer on road. 2 Gale 63-75 34-40 Larger branches break off. Slight structural damage occurs 3 Strong Gale* 76-87 41-47 Roofing dislodged. Stormy: 1 Storm 88-102 48-55 Trees uprooted. Considerable structural damage. 2 Violent Storm* 103-117 53-63 Widespread damage. 3 Hurricane* 118 or 64 or Widespread damage more more 9 D. Sea Condition as Affected by Wind Force WIND FORCE SEA CONDITION Calm Ripples with the appearance of scales are formed but without foam crests. Smooth Small wavelets, still short but more pronounced. Crest have glassy appearance and do not break. Slight Small waves, becoming longer. Fairly frequent white horses. Moderate Moderate waves taking a more pronounced long form. Many white horses are formed-a change of some spray. Rough Large waves begin to form. Sea heaps up and white foam from breaking waves begin to be blown in streaks along the direction of wind. Very Rough Moderately high waves of greater length. Edges of crest begin to break into spindrift. Foam is blown in well-mark streaks along the direction of the wind. High High to very high waves with long overhanging crests. The surface of the sea takes on white appearance. The thumbling of the sea becomes heavy with visibility affected. Very High Exeptionally high waves. Small and medium size ships occasionally lost from view behind waves. The sea is completely covered with long white patches of foam. The edges of wave crest are blown into froth. Phenomenal The air is completely filled with foam and spray. Sea completely white with driving spray. Visibility very seriously affected. Tropical Cyclone Intensity/Category Intensity / Category Maximum Winds Tropical Depression Between 35 KPH and 64 KPH near the center Tropical Storm Between 65 KPH and 118 KPH near the center Typhoon 119 to 200 KPH near the center Super Typhoon Maximum winds greater than 200 KPH 10