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United States Army Aviation Center
Fort Rucker, Alabama
JUNE 2004
STUDENT HANDOUT
TITLE:
WEATHER
FILE NUMBER:
63-0677-5
PROPONENT FOR THIS LESSON PLAN IS:
Aviation Training Brigade
ATTN: ATZQ-ATB-AD
Fort Rucker, Alabama 36362-5000
FOREIGN DISCLOSURE RESTRICTIONS:
This product/publication has been reviewed
by the product developers in coordination with the USAAVNC foreign disclosure
authority. This product is releasable to students from all requesting foreign
countries without restrictions.
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NOTES
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TERMINAL LEARNING OBJECTIVE (TLO):
At the completion of this lesson the student will:
ACTION:
Determine weather requirements for VFR/IFR flights.
CONDITIONS:
While performing instrument flight examiner (IE) duties.
STANDARDS: In accordance with (IAW) FM 1-230 and Department of Defense Flight
Information Publications (DOD FLIP).
SAFETY REQUIREMENTS:
None.
RISK ASSESSMENT LEVEL:
Low.
ENVIRONMENTAL CONSIDERATIONS:
None.
EVALUATION: Each student will be evaluated on this block of instruction by
completing a 50 minute (.9 hour) Criterion Referenced Test. The test consists
of 36 questions divided into 5 scoreable units. Each student must receive a
GO on each scoreable unit to successfully complete the examination.
A.
ENABLING LEARNING OBJECTIVE (ELO) #1:
ACTION:
Identify the weather principles and theory.
CONDITION:
STANDARD:
1.
While performing instrument flight examiner (IE) duties.
IAW FM 1-230.
Learning Step/Activity 1.
The Atmosphere (Chapter 2).
a. The atmosphere is the envelope of air which surrounds the earth.
Approximately ½ of the air, by weight, is within the lower 18,000’. The air
particles, however, become less numerous with increasing altitude until they
gradually overcome the earth’s gravitational force and escape into space.
b. A given volume of dry air contains about 78% nitrogen; 21% oxygen,
and 1% argon, carbon dioxide, and minute amounts of other gases. Natural air
contains, in addition to the gases present in dry air, a variable amount of
water vapor, most of which is concentrated below 30,000’. The maximum amount
of water vapor the air can hold depends primarily on the temperature of the
air; the higher the temperature, the more vapor it can hold.
c. Weather is defined as the state of atmosphere with respect to
temperature, moisture content, turbulence, and cloudiness. These interact in
various combinations to form the following six major meteorological elements:
air temperature, humidity, clouds, precipitation, atmospheric pressure, and
wind.
2.
Learning Step/Activity 2.
a.
Temperature (Chapter 3).
Temperature is a measurement of the amount of heat (Para 3-1).
(1) Different substances have different molecular structures that
absorb, retain, and radiate heat at different rates. Land heats and cools
faster than water.
(2) The earth's surface is heated during the day by incoming solar
radiation called insolation. Heat radiated from the earth by outgoing
radiation is called terrestrial radiation.
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(3)
Fahrenheit and Celsius (centigrade) scales used by aviators.
b. Temperature distribution (Para 3-4) over the earth's surface depends
first on the seasons and second on the composition and distribution of land
and sea surfaces over the earth.
c. Heat transfer (Para 3-5).
another in four different ways.
Heat can be transferred from one body to
(1) Radiation. The transfer of heat by electromagnetic waves.
Heat waves are filtered and absorbed by gases in the atmosphere. When heat
waves are absorbed, the energy is transferred to the absorber, raising its
temperature. Heat waves can also be reflected. Clouds and snowfields are
effective reflectors and reflect 50 to 80 percent of the sun's heat and light
radiation.
(2) Conduction. The transfer of
physical contact between molecules. Air is
only exchanged at the earth's surface where
atmosphere are actually in contact with the
heat energy through direct
a poor conductor of heat. Heat is
the lowest few centimeters of the
ground or water.
(3) Convection. The process of a heated substance carrying heat as
it moves from one place to another. Water heated in a container is warmed at
the bottom, expands, becomes less dense, and rises to the top, bringing heat
with it. The cold water at the top, being denser, sinks to the bottom.
(4) Advection. The term used for the horizontal transport of heat
by wind. Advection moves about 1,000 times more heat in the earth's
atmosphere than convection.
d. Adiabatic process (Para 3-6). The change in the temperature of a
gas which results from a change in pressure without a gain or loss of heat
energy to or from an outside source.
(1) Rising air. When air rises, it is cooled because it is
expanding by moving to an altitude where pressure and density are less, a
process called adiabatic cooling.
(2) Descending air. When the air is forced downward, it is
compressed, causing it to heat, a process called adiabatic heating.
(3) Rising unsaturated air. Cools at the dry adiabatic lapse rate
of 3°C for each 1,000 feet of altitude.
(4) Rising saturated air. Cools at the moist adiabatic lapse rate
of 1.1°C to 2.8°C for each 1,000 feet of altitude. A small decrease in
temperature of ascending saturated air causes a relatively large amount of
moisture to condense as it cools which releases latent heat into the air
slowing the temperature decrease.
(5) Standard lapse rate (Para 3-7a). A basis for calibrating
aircraft instruments and preparing performance charts -2°C for each 1,000 feet
of altitude.
(6) Effects of nonstandard temperature on pressure and density
(figure 3-8). The altimeter reads too high in cold air; you are lower than
altimeter indicates. The altimeter reads too low in warm air; you are higher
than the altimeter indicates.
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(7) Inversion (Para 3-7b). An increase in temperature with an
increase in altitude. The most frequent type inversion is through terrestrial
radiation on a clear night. Inversions are also associated with fronts.
3.
Learning Step/Activity 3.
Moisture (Chapter 4).
a. Water continually evaporates, cools, condenses, and falls to the
earth in various forms of precipitation. This process is called the
hydrologic cycle which keeps moisture in the atmosphere and causes temperature
and pressure changes.
b. States [Para 4-2a(1)]. Water is found in three states, solid,
liquid, and gaseous. The change from one state to another involves the
exchange of heat energy. As the moisture changes state, heat is either
absorbed or released to the environment.
(1) As water changes from solid to liquid to gas or direct from
solid to gas, heat is absorbed.
(2) As water changes from gas-liquid-solid or direct from gas to
solid, latent heat is released.
c. Moisture content (Para 4-3a). At a given temperature there is a
limit to the amount of water vapor the air can hold. When this limit is
reached, the air is saturated. The higher the air temperature the more water
vapor the air can hold. The lower the air temperature, the less water vapor
the air can hold before saturation is reached and condensation occurs.
d. Relative humidity (Para 4-3b). The ratio of the amount of water
vapor in the air to the maximum amount the air can hold when saturated at that
temperature.
e. Dew point (Para 4-4). An indicator of the amount of moisture in the
air. It is that temperature to which air would have to be cooled for
saturation to occur. As the air temperature and dew point spread is within
2ºC (4ºF), the possibility of the formation of fog or low clouds is increased.
f. Precipitation (Para 4-7). Liquid or solid moisture that falls from
the atmosphere in the form of rain, drizzle, ice pellets, snow, or
combinations of these. Occurs when cloud particles grow in size and weight
and fall because of gravitational pull.
4.
Learning Step/Activity 4.
Atmospheric pressure (Chapter 5).
a. Atmospheric pressure is the force-per-unit area exerted by the
weight of a column of air lying directly above a point. It may be expressed
in pounds per square foot (PSF), inches of mercury (Hg), or millibars (MB).
Pressure patterns are shown on weather charts by a series of lines, called
isobars, which connect points of equal pressure and outline pressure areas.
The standard procedure on maps in North America is to draw isobars for every 4
millibars, with intermediate 2 millibar lines as needed.
(1) Low pressure system (Para 5-5a). A pressure system in which
the barometric pressure decreases toward the center and the wind flow around
the system is counterclockwise in the Northern hemisphere. Air flows inward
and up, converges, and cools adiabatically. The cooling increases relative
humidity and produces cloudiness, precipitation, turbulence, strong winds, and
generally poor flying weather. Convergence may also occur in areas where
there are no lows or fronts.
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(2) High pressure system (Para 5-5b). A pressure system in which
the barometric pressure increases toward the center and the wind flow around
the system is clockwise in the Northern Hemisphere. Air flows downward and
out, subsides, and heats adiabatically, relative humidity decreases producing
generally good flying weather. This outflow of air is called divergence.
(3)
Col.
The neutral area between two highs and two lows.
(4) Trough. An elongated area of low pressure, with the lowest
pressure along the trough line. Weather is frequently violent.
(5) Ridge. An elongated area of high pressure with the highest
pressure along the ridgeline. Weather is generally favorable.
b. Pressure gradient (Para 5-6). The rate of change in pressure in a
direction perpendicular to the isobars is called pressure gradient. The
closer the spacing of the isobars, the stronger the pressure gradient and the
stronger the winds.
c. Altimeter (Para 5-7). An altimeter reads accurately only in a
standard atmosphere and when the correct altimeter setting is used. Standard
conditions seldom exist.
(1) The atmospheric pressure frequently differs at the point of
landing from that at takeoff. Adjustment of altimeter may be necessary from
the takeoff point to the landing point.
(2) Error due to variation from standard temperature. An aircraft
flying in warmer than standard air would normally be higher than the altimeter
indicates. Conversely, if the air temperature at flight altitude is colder
than standard air the aircraft will normally be lower than the altimeter
indicates.
d. Density altitude (Para 5-8). Density altitude is defined as the
pressure altitude corrected for temperature deviations for the standard
atmosphere. Density altitude bears the same relation to pressure altitude as
true altitude does to indicated altitude. Pressure altitude is the distance
measured from 29.92” pressure level (The standard datum plain).
(1) Formula for obtaining density altitude from a known pressure
altitude: DA= PA + (120xTv). Where DA = density altitude. PA = pressure
altitude. 120 = temperature constant. Tv = variation of the actual
temperature from standard at the pressure altitude.
(2) Density altitude computation (Para 5-8b). The first step in
computing density altitude is to determine the pressure altitude by setting
the altimeter to 29.92 in the Kollsman window of the altimeter. The second
step is to determine the effect of actual air temperature of the air density.
The standard temperature of the atmosphere is 15 degrees C at sea level with
a decrease of 2 degrees C per thousand feet. Each 1 degree C variation from
standard temperature changes the density altitude approximately 120 feet.
Temperature variation is incorporated into a formula for obtaining Density
Altitude from a known pressure altitude.
5.
Learning Step/Activity 5.
Atmospheric circulation (Chapter 6).
a. Circulation and wind (Para 6-2a). Circulation is the movement of
air over the surface of the earth. Differences in air density and temperature
cause the air to circulate. We identify this circulation as wind.
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b. Semi-permanent pressure areas may be created by local surface
deviations from the primary circulation. These semi-permanent pressure
systems are important in the formation and movement of air masses which
produce frontal systems.
(1) Two high-pressure cells form one over the Pacific Ocean and one
over the Atlantic Ocean near the 30° north latitude.
(2) Two high-pressure cells exist one over Canada (the North
American high) and one over Siberia (the Siberian high) between the 45° to 60°
north latitude.
(3) Two low-pressure cells form the Icelandic and Aleutian low
pressure areas.
c. Secondary circulation (Para 6-6). Consists of atmospheric
disturbances and irregularities in the lower levels of the troposphere brought
about by movement of high and low pressure systems and movement of air within
these pressure systems. These moving systems are smaller than the semipermanent cells of general circulation.
d.
e.
Factors that influence actual circulation.
(1)
Irregular distribution of oceans and continents.
(2)
Heating differences between water and land.
(3)
Irregular terrain.
(4)
Daily variation in temperature.
(5)
Seasonal changes.
Forces affecting air motion (Para 6-7).
(1) Pressure gradient force. The initiating force which produces
wind. The force always acts directly across isobars toward the lower
pressure.
(2) Coriolis force. Perpendicular to the air flow, deflects air to
the right in the Northern Hemisphere, is strongest at the Poles and decreases
to zero at the Equator, and increases as wind speed increases.
(3) Centrifugal force. The centrifugal force that results from the
rotation of the earth neutralizes some of the effect of gravity. The effect
of centrifugal force would cause all air masses to travel directly to the
equator.
(4) Frictional force. Greatest near the ground and tends to retard
air movement and reduce the Coriolis force. The resultant surface wind flows
at an angle of about 30° to 45° to the isobars over land surfaces. Above 2000
feet the effect is negligible. As the frictional force decreases with
altitude the wind speed will increase. Beyond the frictional layer, increases
in wind speed are due to variations in the pressure force with altitude.
6.
Learning Step/Activity 6.
Stability (Chapter 7).
a. Stability is the atmosphere's
depends on the vertical distribution of
Hotter air is lighter (less dense) than
than dry air. If air is warmer or more
resistance to vertical motion. It
the air's temperature and moisture.
colder air and moist air is lighter
moist than its surroundings, it is
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unstable and will rise. If the air is colder or drier than its surroundings,
it is stable and will sink. The degree of stability of the atmosphere helps
determine what type clouds, if any.
b.
Absolute Stability (Para 7-4b). A parcel of absolutely stable air
which is lifted becomes cooler than the surrounding air and sinks back to its
original position as soon as the lifting force is removed.
c.
Absolute Instability (Para 7-4d). A parcel of air lifted even
slightly will at once be warmer than its surroundings: and, like a hot air
balloon, it will be forced to rise rapidly.
B.
ENABLING LEARNING OBJECTIVE (ELO) #2:
ACTION:
masses.
Identify the classification and characteristics associated with air
CONDITION:
STANDARD:
1.
While performing instrument flight examiner (IE) duties.
IAW FM 1-230.
Learning Step/Activity 1.
General (Chapter 9).
a. Air masses (Para 9-1). A large body of air (1,700 KM or more
across) whose physical properties (temperature and humidity) are horizontally
uniform.
b.
Characteristics of an air mass (Para 9-2).
(1) High pressure areas stagnate over large uniform surfaces called
source regions. Typical surfaces regions include: large uniform land areas,
ice caps, snow fields, and large bodies of water. The air assumes the
temperature and moisture characteristics of the surface.
(2) Some semi-permanent, seasonally migrating air masses are
associated with low pressure areas. Examples are the air masses associated
with the heat at the equator and those associated with large desert areas.
c. Classification (Para 9-3). Air masses are classified with a three
letter identifier indicating the temperature, moisture content, and stability
of the air.
(1) Moisture content [Para 9-3a(2)]. A lower-case letter indicates
the type source region of the air mass. A land-source air mass produces dry
air and is designated by the small letter “c” to indicate a continental air
mass. A water-source air mass produces moist air and is designated by the
small letter “m” to indicate a maritime air mass.
(2) Temperature is identified by the source region [Para 9-3a(1)].
Capital-letter abbreviations which identify the latitude of the source region
are used to indicate the air mass temperature. The following designations
identify air masses that frequently affect the northern temperate zone:
(a)
A = Artic air mass (70º to 90º Latitude).
(b)
P = Polar air mass (40º to 60º Latitude).
(c)
T = Tropical air mass (10º to 30º Latitude).
(d)
E = Equatorial air mass (0º to 10º Latitude).
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(3) Stability (Para 9-3b). A lower-case letter indicates the
temperature of the air relative to the temperature of the surface beneath
which indicates stability or instability.
from below.
(a) Warm "w". Air is warmer than surface beneath it, cooled
This is generally a stable air mass.
(b) Cold "k". Air is colder than surface beneath it, heated
from below. This is generally an unstable air mass. The letter "k" comes
from the German word "kalt," meaning cold.
d. General characteristics of air masses (Para 9-5).
of typical air masses with which they are identified.
Weather condition
(1) Cold air mass (k). The amount and severity of the clouds,
precipitation, and associated weather depends on the amount of moisture in the
air mass. Air is colder than the surface beneath it and is heated from below.
The heated air expands, rises, and is unstable. The vertical currents
associated with the rising air result in the following types of weather.
(a)
Cumulus and cumulonimbus type clouds.
(b)
Generally good (high) ceiling (except in precipitation
(c)
Excellent visibility (except in precipitation areas).
areas).
(d) Pronounced air instability (turbulence) in lower levels
due to convective currents.
(e)
Occasional local thunderstorms, heavy showers, hail, or
snow flurries.
(2) Warm air mass (w). The amount of clouds and precipitation
depends on the amount of moisture in the air mass. Air is warmer than the
surface beneath it, cooled from below. The cooled air would have no tendency
to rise and is stable. The absence of vertical currents results in the
following types of weather:
(a)
Stratus and stratocumulus type clouds and/or fog.
(b)
Low ceilings (often below 1000’).
(c)
Poor visibility (since haze, smoke, and dust are held in
(d)
Smooth stable air with little or no turbulence.
lower levels).
2.
Learning Step/Activity 2.
9-7).
Air masses affecting the United States (Para
a. General. As the different air masses migrate across the United
States, typical weather conditions can be expected in each type air mass.
Local influences, such as mountains, lakes, etc., can alter these conditions.
(1) Maritime polar (mP)(Para 9-8) air masses arrive in the US from
two different source regions, the North Pacific Ocean and the North Atlantic
Ocean.
(a) Winter – Pacific Coast [Para 9-8a(1)]. Originate in the
interior of Siberia. They have a long over water trajectory and become
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unstable in the lower levels. As they enter the US they are cooled from below
and become more stable with stratus and stratocumulus clouds. As they move
eastward up the slopes of the mountains, they form cumuliform clouds with
extensive shower activity. East of the mountains, the air descends and is
warmed with decreased humidity and clear skies.
(b) Winter - Northeast Coast [Para 9-8a(2)]. As the move
into the New England States from the northeast, they are usually colder and
more stable than those entering the West Coast from the northwest direction.
Low stratiform clouds with light continuous precipitation and generally strong
winds.
(c) Summer (Para 9-8b). Since water temperatures are cooler
than the adjacent land temperatures in the summer, maritime polar air masses
entering the Pacific Coast become unstable because of surface heating. In the
afternoon, cumuliform clouds form and scattered showers occur. At night, fog
and low stratiform clouds are common on the coastal regions.
(2) Continental polar (cP)(Para 9-9) air is cold and dry, and their
source region is very stable. Originate over Canada and Alaska.
(a) Winter. As they enter the United States from central or
western Canada, they are heated by the underlying surface. During daylight
hours, the air is generally unstable near the surface and the sky is usually
clear. At night the air becomes more stable. As the air passes over the warm
water of the Great Lakes, it acquires heat and moisture and becomes unstable
in the lower levels. Cumuliform clouds form and produce snow over the lakes
and on the leeward side of the lakes. Cumuliform clouds intensify at the
Appalachians with unfavorable flying conditions.
(b) Summer (Para 9-9b). These air masses are warmer and
contain more moisture; the air is less stable in the surface layers.
Scattered cumuliform clouds form during the day and dissipate at night when
the air becomes more stable.
(3) Maritime Tropical (mT)(Para 9-10). Originate over the Atlantic
Ocean, the Gulf of Mexico, and the Caribbean Sea. More common in the
Southeastern US. They bring warm moist stable air.
(a) In the winter the land is colder than the water. Warm
moist air masses are cooled from below and become stable as they move inland
over the south Atlantic and Gulf States. Fog and Statiform clouds form at
night and tend to dissipate during the afternoon.
(b) In the summer the land is normally warmer than the water;
the air moves inland and is heated from below by the land and becomes
unstable. Along the coast, stratiform clouds are common during the morning,
change to cumuliform by late morning, and thunderstorms by late afternoon.
(4) Continental Tropical (cT)(Para 9-11). Source region MexicoTexas-Arizona-New Mexico area and only in the summer. Characterized by high
temperatures, low humidity, and, although rare scattered cumuliform clouds.
Flying is often rough especially during the daylight hours. Occasional dust
storms may extend to altitudes in excess of 10,000 feet and reduce visibility
for many hours.
C.
ENABLING LEARNING OBJECTIVE (ELO) #3:
ACTION: Identify the types of fronts to include the associated weather
phenomena.
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CONDITION:
STANDARD:
1.
While performing instrument flight examiner duties.
IAW FM 1-230.
Learning Step/Activity 1.
General (Para 10-1).
a. Fronts are transition zone (boundaries) between air masses of
different density. The density of the air is primarily controlled by the
temperature of the air. Types: Cold, Warm, Stationary, and Occluded.
b. Air Mass discontinuities (Para 10-2). A front is a boundary in the
atmosphere along which certain physical properties between the air masses are
discontinuous. Discontinuities are used to identify a front and determine its
location.
2.
(1)
Temperature change.
(2)
Wind shift (Approximately 90º).
(3)
Pressure tendency (falling then rising).
(4)
Dew point change.
Learning Step/Activity 2.
Cold front (Para 10-3).
a. Cold front is the leading edge of an advancing mass of relatively
cold air. The colder air mass is denser and under rides the warmer air
forcing it upward. The frontal slope will be quite steep as compared to other
type fronts with a range of 1:50 to 1:150 depending on the forward speed of
the front. A typical slope is 1:80.
b.
Cold front characteristics (Para 10-3b).
(1) Wind ahead of the front is generally from the southwest and
behind the front is from the northwest.
(2)
Warm air ahead of the front and cold air behind the front.
(3) Due to surface heating weather band of cumuliform clouds
develop 50 to 100 mile in width at the frontal boundary. With rapid moving
cold fronts, a prefrontal squall line may form up to 300 miles ahead of the
surface front.
(4) Direction of movement is generally from northwest to southeast
with average speed 22 knots and slope ratio of 1 to 80.
(5) The colder air behind the front will have lower dew points
where the warmer air ahead of front will have a higher dew point. Even in
exceptional temperature situations, a distinct dew point change should occur
across a front.
c
Cold frontal weather depends upon the amount of moisture in the warm
air and the steepness of the slope. If the warm air is comparatively dry, no
appreciable clouds and precipitation would occur. If the warm air has high
moisture content and a steep frontal surface, expect the following typical
weather pattern.
(1)
Narrow weather band.
(2) Rapid lifting of the warm air causes towering cumulus and
cumulonimbus clouds.
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(3) Thunderstorms with associated hazards including: heavy rain
showers, gusty surface winds, extreme turbulence aloft, lightning, hail, and
possible tornadoes.
(4) Squall lines which are instability lines may develop ahead of
fast moving cold fronts. The line may be solid or broken and consist of
towering cumulus and cumulonimbus clouds with rain showers, thunderstorms and
possible tornadoes.
3.
Learning Step/Activity 3.
Warm front (Para 10-4).
a. The air mass boundary formed between the trailing edge of the
retreating mass of cool air and the warm air mass moving in to replace it, is
a warm front. The advancing warm air is less dense than the retreating colder
air and overrides the colder air.
b.
Warm front characteristics (Para 10-4b).
(1) Wind ahead of the front is from the southeast and warm sector
behind the front is from the southwest.
(2)
As the front passes a location the temperature increases.
(3) With the warm air riding over the slope of the cooler air
stratiform clouds develop. They will range from nimbostratus at the front to
cirrus as far as 1,000 miles ahead of the front. An area of rain can extend
as far as 300 miles ahead of the front. The typical warm front is
characterized by wide area stratiform clouds with low ceiling and poor
visibility.
(4) Warm front usually moves from southwest to northeast at an
average speed of 10 knots.
(5) The slow speed of movement is due to opposing wind components.
The average slope ratio of the warm frontal surface is 1 to 200.
c. Warm frontal weather depends primarily upon the amount of moisture
and stability of the warm air mass and the steepness of the frontal slope. If
the warm air mass is comparatively dry, no appreciable clouds or precipitation
occurs. If the warm air has high moisture content, expect the following
typical weather pattern.
(1) Wide weather band ahead of the surface position of the warm
front can be hundreds of miles. Gradual overriding of the warm air producing
predominately stratiform clouds.
(2) Precipitation normally in the form of drizzle, light rain, ice
pellets, freezing rain, and snow.
(3) Hazards, including low ceilings and visibility, rime icing in
clouds, clear icing in freezing rain, and possibility of embedded
thunderstorms.
4.
Learning Step/Activity 4.
Occluded front (Para 10-5).
a. Occluded front is the portion of the surface front where the fast
cold front has overtaken the warm front. The warm front is lifted off the
surface. There are two types of occlusions: cold front occlusions and warm
front occlusions.
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b.
Occluded front characteristics.
(1) If the air behind the cold front is colder than the air ahead
of the warm front, the warm front will be lifted. This is called a cold front
type occlusion.
(2) If the air ahead of the warm front is colder than the air
behind the cold front, the cold front will ride over the warm front surface.
This is called a warm front type occlusion. A line of imbedded thunderstorms
is often associated with a warm front occlusion within an overcast sky.
(3) Weather in an occluded front is a combination of cold and warm
frontal weather.
(4) The most severe weather associated with an occluded front is 50
to 100 miles north of the surface apex of the three fronts.
5.
Learning Step/Activity 5.
Stationary front (Para 10-6).
a. The boundary between different air masses with little or no movement
(less than 5 knots) is called a stationary front. The wind on each side of
the front generally parallel each other, but are opposite in direction.
b. The associated weather is primarily of the warm front type except
when the air is unstable and the stationary front is slowly moving southward.
In this case, the associated weather resembles cold frontal weather.
c. The possibility exists of a closed, low pressure system forming
which could develop later into an occluded front.
D.
ENABLING LEARNING OBJECTIVE (ELO) #4:
ACTION:
Identify the conditions that produce weather hazards to flight.
CONDITION:
STANDARD:
1.
While performing instrument flight examiner duties.
IAW FM 1-230.
Learning Step/Activity 1.
Turbulence (Chap 11).
a. Causes of turbulence (Para 11-2). Caused by random fluctuations of
airflow which are instantaneous and irregular. The four degrees of intensity
are light, moderate, severe, and extreme.
b.
Turbulence will be divided according to the following causes:
(1) Thermal causes (Para 11-3). Localized vertical convective
currents due to surface heating or unstable lapse rates and cold air moving
over warmer ground or water.
(a)
Normally extends to about 3,000 feet AGL - can be higher.
(b)
Generally light to moderate - can be severe.
(2) Mechanical causes (Para 11-4).
over irregular terrain or obstructions.
Resulting from wind flowing
(a) When the air near the surface of the earth flows over
obstructions, irregular terrain (bluffs, hills, mountains) and buildings, the
normal horizontal wind flow is disturbed.
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(b) Mountain wave turbulence. Formed in stable air with wind
flow of 25 knots or more perpendicular to a mountain range. The stronger the
wind, the larger the wave. One or more waves may form on the leeward side of
the mountains.
1. Presence of a mountain wave may be indicated by cap
clouds at the peak of the mountain and roll and lenticular clouds on the
leeward side.
2. Areas of steady updrafts and downdrafts may extend to
70,000 feet and as far as 300 miles downwind from the mountain range.
Moderate to severe turbulence can be encountered in these waves.
(3) Frontal causes (Para 11-6). Frontal turbulence is caused by
lifting of warm air by a frontal surface, leading to instability and/or mixing
or sheer between the warm and cold air masses.
(4) Wind shear causes (Para 11-7). Wind shear is a change of wind
speed and/or direction over a short distance. A relatively steep gradient in
wind velocity along a given line of direction (either vertical or horizontal)
and produces churning motions (eddies) which result in turbulence. It is
often referred to as clear air turbulence (CAT).
(a)
Generally associated with jet streams (strong winds of 50
(b)
Hard to forecast or detect until encountered.
(c)
Can produce extreme turbulence.
knots or more).
2.
Learning Step/Activity 2.
Thunderstorms (Chapter 12).
a. Thunderstorm formation (Para 12-2). The minimum factors essential
to the formation of a thunderstorm are conditionally unstable air with
relatively high moisture content and some type of lifting action.
b.
Stages of a thunderstorm (Para 12-5b).
(1) Cumulus stage. The chief distinguishing feature of the cumulus
or building stage is an updraft (3,000 to 6,000' FPM) that prevails throughout
the entire cell. Turbulence will light to severe. Temperature will be warmer
in the cloud. Icing will be clear and rime at the appropriate levels.
(2) Mature stage. The beginning of surface rain and adjacent
updrafts and downdrafts initiates the mature stage and is considered the most
dangerous. Precipitation amounts may be heavy with the possibility of hail.
With the up and down draft creating wind shear, turbulence levels will be
severe to extreme. High wind and first gust may be found in any sector,
usually 10 to 20 miles from the storm. Wind speeds average about 15 knots
above prevailing velocity with about a 40° change in direction. Speed may be
75 knots or more. Icing can be expected
Icing (clear and rime) can be
expected at different levels above the freezing level. Lightning will be at
its maximum at freezing level. Cloud tops extend up to 40,000 feet, sometimes
in excess of 70,000 feet.
(3) Dissipating stage. As the updraft begins to weaken the
downdrafts continue to build in area until the storm is mostly downdrafts.
Turbulence levels are light to moderate. Precipitation is light to none.
Icing will be clear and rime at the appropriate levels.
c.
Steady state thunderstorms.
D-16
(1) In a steady state thunderstorm, precipitation falls outside the
updraft allowing the updraft to continue unabated. This allows the mature
stage updrafts to become much stronger and last much longer than the normal
air mass storm. Such a cell may last for several hours.
(2) Such storms usually are associated with weather systems such as
fronts, converging winds, troughs aloft, and often form into squall lines.
d. Thunderstorm hazards.
thunderstorms.)
(Solicit student experiences with
(1)
Heavy rain and/or snow possible tornadoes.
(2)
Hail and structural damage.
(3)
Icing.
(4)
Lightning, instrument error, loss of communications, and
(5)
Severe surface gusts and low level wind shear.
(6)
Pressure variations.
(7)
Low ceiling and visibility in rain showers.
(8)
Turbulence - greatest hazard - light to extreme.
static.
e. Recommended flight procedures (Para 12-8). Avoid all thunderstorms.
AR 95-1 - Aircraft will not be intentionally flown into thunderstorms.
f.
g.
3.
Microburst formation and hazards.
(1)
Evolution of a microburst.
(2)
Symmetric microburst.
(3)
Asymmetric microburst.
(4)
Dry microburst.
Weather evaluation to avoid thunderstorms.
(1)
METAR and Terminal aerodrome forecasts (TAF).
(2)
Aviation severe weather watch.
(3)
LLWAS.
(4)
Convective SIGMETs.
(5)
Visual cues.
(6)
PIREPs.
(7)
Weather radar.
Learning Step/Activity 3.
Icing (Chapter 14).
D-17
a. Factors necessary to produce structural icing on aircraft in flight
are free-air temperature at or below freezing (±4ºC to -20ºC) and presence of
visible liquid moisture in the form of clouds or precipitation (Para 14-2).
Intensity levels are reported as trace, light, moderate, and severe.
b.
Types and characteristics (Para 14-8).
(1)
Clear icing - most hazardous.
(a)
Formed from large super-cooled water droplets.
(b) Forms as clear, dense, or solid ice, out and back from
the leading edge of the airfoil as a blunt shape and is hard to break loose,
cohesive.
(c)
Found in cumuliform clouds between temperatures 0°C to
-10°C.
(d) Found in liquid precipitation at temperatures lower than
0°C as freezing rain (usually associated with warm fronts).
(2)
Rime icing - most common.
(a)
Formed from tiny super-cooled water droplets.
(b) Forms as granular, opaque, and rough deposit of ice and
extends outward from leading edge of airfoils.
(c)
More brittle and easier to dislodge than clear ice.
(d) Found in stratiform clouds at temperatures 0°C to -20°C
and cumuliform clouds at temperatures -10°C to -20°C.
(3)
Frost.
Sublimation of water vapor to ice crystals.
(a) Generally formed on clear nights when the metal of the
aircraft is radiation cooled to temperatures below 0°C.
(b) Can be formed when an aircraft descends from temperatures
below 0°C to warmer humid air.
(c)
Causes loss of lift and collecting agent for other types
(d)
Should be removed before takeoff.
of icing.
c. Aircraft icing is more probable and severe over mountainous or steep
terrain than over low or flat elevations. The presence of a mountain range
causes strong upward air currents on its windward side which are capable of
supporting larger than average water droplets, thereby compounding the icing
hazard. Severest icing occurs above the crest and to the windward side of the
ridges. This zone usually extends 4,000 to 5,000 feet above the mountain and
can go higher in cumuliform clouds.
d. Effects of icing on aircraft (Para 14-10). Ice can cause mechanical
or visual obstruction. It may modify the profile of part of the aircraft,
reducing its aerodynamic efficiency. Ice can alter the frequency of some
parts of the aircraft (vibration may be induced). Ice may break off and cause
serious mechanical damage, asymmetric condition for rotor mechanism, or injury
to nearby persons.
D-18
e.
Recommended flight procedures.
(1)
Remove all ice and snow from the aircraft before takeoff.
(2)
Use all necessary anti-icing/deice equipment.
(3) Avoid flying in clouds when the outside air temperature is
between 0ºC and -20ºC.
(4) If ice is encountered, climb or descend to an altitude where
the temperature is warmer than 0ºC or colder than -20ºC.
4.
Learning Step/Activity 4.
Fog (Chapter 15).
a. Fog is minute water droplets or ice crystals suspended in the
atmosphere with no visible downward motion. Fog is similar to stratus clouds.
The base of fog is at the earth's surface and the base of a cloud is at least
50 feet above the surface. Fog is hazardous because it restricts surface
visibility.
b.
Fog formation (Para 15-2).
(1) High relative humidity (By adding moisture to the air or
cooling to the dew point).
(2) Light wind less than 5 knots for mixing action (spreads surface
cooling action).
(3)
c.
Fog types (Para 15-4).
(1)
surface.
Condensation nuclei.
Radiation fog.
Radiation cooling with light wind.
(2) Advection fog. Movement of warm moist air over a colder
If fog forms over the ocean, it is referred to as sea fog.
(3) Upslope fog.
and cools by expansion.
Moist stable air flows up a sloping land surface
(4) Valley fog. In the evening cold dense air accumulates in the
valleys causing the air temperature to decrease to dew point temperature.
(5) Ice Fog. At temperatures of -25 and below, water vapor
sublimates into ice crystal without passing through a liquid state.
(6)
Evaporation fog.
Moisture added to the air.
(a) Frontal fog. Forms when precipitation falls from the
maritime tropical systems and evaporates in the polar air below. Common with
slow moving winter frontal systems and active warm fronts during all seasons.
(b) Steam fog. Cold stable air flows over a non-frozen water
surface that is several degrees warmer than the air. Evaporation of moisture
into the cold air saturates the air.
E.
ENABLING LEARNING OBJECTIVE (ELO) # 5:
ACTION:
Decode METAR and TAF reports.
CONDITION:
While performing instrument flight examiner duties.
D-19
STANDARD:
1.
IAW FM 1-230 and DOD FLIP.
Learning Step/Activity 1.
Aviation routine weather reports (METAR).
a. Aviation routine weather reports (METAR) is the observation code to
report meteorological data. METAR was internationally for worldwide use but
each country can modify the code. When METAR data is missing, it is simply
omitted. (AIM and DOD FLIP).
b.
The following describe the elements in a METAR report:
(1) Report type. METAR is a scheduled observation taken between
55-59 minutes past the hour (hourly observation). SPECI (special report is an
unscheduled observation taken when a predefined condition criteria change
occurs.
(2) ICAO station identifier.
station identifiers.
The METAR code uses ICAO 4-letter
(3) Date and time of report. The date and time the observation is
taken are transmitted as six-digit date/time group appended with Z to denote
UTC. The first two digits are the date followed with two digits for hour and
two digits for minutes.
(4) Modifiers (As required). “AUTO” identifies a METAR/SPECI
report as an automated weather report with no human intervention. “COR”
indicates a corrected report that is sent out to replace an earlier report
with an error. AO1 is an ASOS without a rain vice snow discriminator and AO2
has a discriminator.
(5) Wind. Reported as 5 digit group (six if over 99 Kts).
Reference to true north, reported to nearest 10 degrees or “VRB” is direction
is variable. If the wind is gusty it is reported as a “G” after the speed
followed by the highest gust reported. The abbreviation “KT” is appended to
denote the use of knots for wind speed.
(6) Visibility. Prevailing visibility is reported in statute miles
with “SM” appended to it. Overseas locations use meter vice statue miles with
9999 (7 SM or greater) as the largest value.
(a) Prevailing visibility is the greatest distance that can
be seen over at least one half of the horizon, not necessarily continuous.
(b) Variable/Sector visibility shown in the Remarks (when
prevailing visibility is less than three miles).
(c) Visibility less than three miles is reported in fractions
of a mile (smallest fraction - 1/16). Visibility between 3 and 15 miles is
reported to the nearest mile. Visibility greater than 15 miles is reported to
the nearest 5 miles.
(7) Runway visual range. “R” identifies the group followed by the
runway heading “/” and the visual range if feet (meters in other countries)
followed with “FT” (i.e. R06/4000FT). M is RVR less than lowest reportable
sensor value, P is greater than highest value, and V means RVR is variable.
(8) Significant weather is reported in the format: Intensity,
Proximity, Descriptor, Precipitation, Obstruction to visibility, and Other.
Reported whenever phenomena are occurring at the time of report in the order
D-20
of predominance of effect on visibility or ceiling.
to decode.
(9)
See weather table in FIH
Sky condition is reported in hundreds of feet above the surface
(AGL).
(a) The amount of sky cover is reported in eights of sky
cover (cumulative), using the contractions:
1.
SKC:
clear (no clouds).
2.
FEW:
few (0/8 to 2/8).
3.
SCT:
scattered (3/8 to 4/8).
4.
BKN:
broken (5/8 to 7/8).
5.
OVC:
overcast (8/8).
(b) Ceiling. The heights above the earth’s surface of the
lowest layer of clouds or obscuring phenomena that is reported as “broken,”
“overcast,” or “obscuration,” and is not classified as thin or partial.
Vertical visibility (indefinite ceiling) is preceded by “VV” and followed by
three digits indicating the vertical visibility in hundreds of feet. When the
ceiling is variable, the remark “CIG” will be shown followed by the lowest and
highest ceiling heights separated by a “V.”
(c)
Suffixed by CB or TCU - cumulonimbus or towering cumulus
when present.
(10) Temperature and dew point are reported two, two digit groups in
degrees Celsius, separated by a “/”. Temperatures below zero are prefixed
with an “M.” If the temperature is missing, the group is omitted.
(11) Altimeter setting is reported in a four digit format in inches
of mercury prefixed with an “A” to denote the units of pressure.
(12) Remarks group will be included in all observations, when
appropriate. The “RMK” denotes the start of the remarks section. There are
two categories of remarks: (1) Automated, manual, and plain language; (2)
Additive and automated maintenance data. See remarks table in FIH.
2.
Learning Step/Activity 2.
Automated weather observation system (AWOS).
a. AWOS is a real time system consisting of various sensors, a
processor, a computer generated voice subsystem, and transmitter to broadcast
local minute-by-minute weather directly to the aircraft.
b. AWOS observations derived from an automated system will include the
prefix “AWOS.” If augmented by certified observer, AWOS augmentation will be
identified as “OBSERVER WEATHER.” The reported visibility is derived from a
sensor near the touchdown of the primary instrument runway and may differ from
prevailing visibility. The reported sky condition/ceiling is derived from the
ceilometer and may differ from the Observer sky condition.
c.
There are four operational levels of AWOS.
(1)
AWOS-A - reports only altimeter setting.
(2) AWOS-1 - reports altimeter setting, wind data, temperature, dew
point, and density altitude.
D-21
(3)
AWOS-2 - reports information in AWOS-1 plus visibility.
(4)
AWOS-3 - reports information in AWOS-2 plus cloud and ceiling
data.
d. The information is transmitted over a discrete radio frequency or
the voice portion of a local NAVAID. Some locations can be received by
telephone. The system transmits a 20 to 30 second weather message each
minute. The messages are updated each minute. Receivable to a maximum of 25
NM at or above 3,000' AGL up to 10,000' AGL.
3.
Learning Step/Activity 3.
Automated surface observation System (ASOS).
a. ASOS is the primary surface weather observing system of the United
States. A joint effort of the National Weather Service, the FAA and the
Department of Defense. The ASOS provides continuous minute-by-minute
observations. Generates information for an aviation routine weather report.
b. Transmits over a discrete VHF radio frequency or the voice portion
of a local NAVAID. Maximum of 25 NM and 10,000' AGL. The ASOS report without
human intervention will contain only that weather data capable of being
reported automatically. “AUTO.”
c. METAR format will be used on AWOS/ASOS sequence. METAR remark
section will contain the type and number of sensors. A01 - Without
precipitation discriminator. A02 - With precipitation discriminator.
4.
Learning Step/Activity 4.
Terminal Aerodrome Forecasts (TAF).
a. A concise statement of the expected meteorological conditions at an
airport during a specified period (usually 24 hours). Scheduled four times
daily for 24-hour periods beginning at 0000Z, 0600Z, 1200Z, and 1800Z.
b. There are two types of TAF issuances: Routine forecast (TAF) and
Amended forecast (TAF AMD). Corrected (COR) or delayed (RTD) TAF’s are
identified only in the communications header which precedes the actual
forecasts.
c. The TAF code uses ICAO 4-letter identifiers as described in the
METAR section. Date and time of origin when the forecast is actually
prepared. The format is a two digit date and four digit time followed by the
letter “Z.”
d. Forecast Meteorological Conditions. Basic Format: Wind, Visibility,
Weather, Sky Condition, and Optional data (i.e. Wind shear). If a
significant, lasting change in any of the elements is expected during the
valid period, a new time period with the changes is included.
c. Forecast change indicators are used when a rapid, gradual, or
temporary change is expected in some or all of the forecast meteorological
conditions.
(1) From (FM) group is used when a rapid change (less than 1 hour)
in prevailing conditions is expected. Appended to the “FM” indicator is the
four-digit hour and minute the change is expected to begin and continues until
the next change group or the end of the current forecast. Generally will
start a new line and contains all the required elements - wind, visibility,
weather, and sky condition.
D-22
(2) Becoming (BECMG) group is used when a gradual change in
conditions is expected over a longer time period (2 hours). Time period when
the change is expected is a four-digit group with the beginning hour and
ending hour of the change period following the “BECMG” indicator. Only the
changing forecast meteorological conditions are included.
(3) Temporary (TEMPO) group is used for any conditions in wind,
visibility, weather, or sky condition which are expected to last for generally
less than an hour at a time, and are expected to occur during less than half
the time period. “TEMPO” followed by a four-digit group giving the beginning
hour and ending hour of the time period during which the conditions are
expected. Only the changing forecast meteorological conditions are included.
(4) Probability forecast is the probability or chance of
thunderstorms or other precipitation events occurring, along with associated
conditions (wnd, vis, sky cond.). “PROB” followed by a two digit percentage
(30 = 30-39%), then the beginning hour and the ending hour the thunderstorms
or precipitation expected.
D-23
APPENDIX E
WEATHER
STUDY GUIDE
1.
Air masses are formed by large bodies of air stagnating over a uniform
surface and acquiring the temperature and moisture characteristics of the
surface. Which type pressure system (high) (low) would be more conducive to
the formation of an air mass?
2.
The relative moisture content of air masses is denoted by classifying
them according to their type source region.
(m)
and (c)
.
3.
Air mass temperature classification, using source regions, from the
coldest to the hottest are —
A
, P
, T
, and E
.
4.
The “w’ classifier for air masses means the air is (colder, warmer)
_________ than the surface beneath it.
5.
The “k” classifier for air masses means the air is being (heated,
cooled) ____________ from below and is (stable, unstable) _____________.
6.
T F A maritime tropical (mT) or continental tropical (cT) air mass
will always be classified as a “w” air mass.
7.
T F A cP mass, after having traveled a long distance over northern
waters, would be redesignated as mP.
8.
List the general weather conditions that would be expected with a “k”
and “w” classification.
“k”
________
“w”
________
Precipitation: ________
________
Ceilings:
________
________
Visibility:
________
________
SFC winds:
________
________
Turbulence:
________
________
Cloud type:
9.
When an air mass is lifted (frontal or terrain), the temperature will
(increase, decrease) _______________ and the relative humidity will (increase,
decrease) _____________.
10.
T
F
cP air masses move farther south during winter than summer.
11. T F When mT air masses dominate the Fort Rucker area in the summer,
the stability classifier during the day will be “k” and thunderstorms are
possible.
12. T F The major hazard associated with cT air masses is clear air
turbulence.
13. T F The trajectories of a cold front in the southeastern United States
are generally to the southwest.
E-1
14. The term “front” normally refers to the boundary between air masses of
different _________________.
15.
The frontal surface always slopes over the (cold, warm) _______air mass.
16. The (leading, trailing) _____________ edge of advancing polar air masses
are called (cold, warm) _____________ fronts in the northern hemisphere, and
they generally move toward the (northeast, southeast) ____________.
17. Squall lines sometimes form (ahead, behind) __________ of fast moving
(cold fronts, warm fronts) ___________________.
18. The slope of a typical cold front is (steep, shallow) ___________ and
the associated band of weather is (wide, narrow) _______________.
19. The type clouds that form with typical cold fronts are predominantly
(stratiform, cumuliform) ______________________.
20.
What are the four elements of discontinuity across a front?
a.
_________________________________________
b.
_________________________________________
c.
_________________________________________
d.
_________________________________________
21. In order to stay on course after penetration of a cold front, a heading
correction to the (left, right) ____________ should be made.
22. The trailing edge of a retreating cold air mass is called a __________
front and generally moves toward the (northeast, southeast) _____________.
23. The weather band associated with a warm front is generally (wide,
narrow) ___________; the associated clouds are primarily (cumuliform,
stratiform) ______________; and predominate (ahead, behind) _____________of
the surface position of the front.
24.
List four hazards to aviation associated with a warm front.
_________________, ____________________,
_________________, ____________________.
25. What type front extends northeastward from the apex and contains the
worst elements of both a cold front and a warm front to include embedded
thunderstorms? _____________________
26. The front that moves at five knots or less is a (cold, warm, stationary)
____________ front.
27. After a cold front passes, the temperature will (increase, decrease)
_______________ and the pressure will (rise, fall) __________.
28.
A front depicted in red with smooth bumps is a ___________ front.
29. Any precipitation that might occur in conjunction with a warm front
would probably be (light or heavy) _________, but it would probably be more
continuous.
E-2
30. The most severe weather associated with an occluded front would be to
the ______________ (give geographic direction) of the apex of the front.
31.
The greatest possibility of frontal fog exists with a ________ front.
32. The clear skies after frontal passage are probably a result of a (cold,
warm) __________ front.
33. Increasing cloudiness from what type of clouds can be expected in
advance of a cold front ___________.
34. The hazards of a fast moving cold front include the formation of a
_____________ line.
35. Listed below are characteristic features of either clear or rime ice.
To the left of each feature, write “C” if it pertains to clear ice, “R” if it
pertains to rime ice, and “B” if it pertains to both types.
a.
b.
c.
d.
e.
f.
g.
______
______
______
______
______
______
______
0ºC to -10ºC in cumuliform clouds.
Formed by freezing rain or drizzle.
0ºC to -20ºC in stratiform clouds.
Should be avoided whenever possible.
Milky, granular-type ice.
-10ºC to -20ºC in cumuliform clouds.
causes loss of lift.
36. T F Ice will not form on the propeller, rotor blades, or rotor head
during flight.
37. When encountering freezing rain, you should expect temperatures above
you to be (warmer, colder) _________.
38. The extreme turbulence associated with mountain waves are found on the
(windward, leeward) side of the mountain.
39. In which stage of thunderstorm development should the most severe
turbulence be expected? ______________________________
40. T F Turbulence in a thunderstorm can be avoided by penetration at an
altitude between 4,000 feet and 6,000 feet AGL.
41. METAR is a scheduled observation taken between ________________ minutes
past the hour (a.k.a. hourly observation).
42. How much sky coverage (or obscuration) is indicated by each of the
following contractions?
a.
b.
c.
d.
e.
SKC
FEW
SCT
BKN
OVC
__________________
__________________
__________________
__________________
__________________
43. A ceiling is defined as the (lowest, highest) ____________ condition
reported that is either ____________or __________ or ___________________.
44.
T
F
Only 1/8 of clouds at a given level may constitute a ceiling.
45. At a certain weather station, the observer notes that to the northeast
he/she can see 3/4 of a mile, to the southeast 1/2 mile, to the southwest 2
E-3
miles, and to the northwest 1/4 of a mile. The observer would report the
prevailing visibility at this station as _________ mile.
NOTE:
Use the following METAR to answer questions 45 through 50.
METAR KCBM 111555Z 15015G30KT 3/8SM +TSRA FEW002 SCT006 OVC010CB 20/18 A2989
RMK TSRAB45
SPECI KNMM 111615Z 19025G35KT 1/2SM TSRA BKN007CB 20/18 A2990 RMK SQ50KT RVNO
TSB50
46.
METAR report for KCBM was transmitted at ___________________.
47.
What is the ceiling at Columbus AFB (KCBM)?
48.
What weather is occurring at Meridian NAS (KNMM)?
49.
What type of clouds are at the ceiling level at Meridian (KNMM)?
50.
What is the temperature/dew point spread at Columbus AFB (KCBM)?
51.
What is the complete wind information at NAS Meridian (KNMM)?
NOTE:
Use the following ICAO METARs to answer questions 51 through 57.
METAR PAED 012155 27005KT 2100 SN OVC080 M10/M15 A3005 RMK CIGM080 FROPA 2100
METAR PAFB 012155 00000 CAVOK M29/M35 A3125.
SPECI PWAK 012115 18010G30KT 9999 +TSRS BKN025 24/21 A2967 RMK CIGM025 CIG
RGD.
METAR PGUA 012155 VRB05KT 0350 -RAFG VV005 30/30 A2944 RMK CIGW005 FG LYR NE
METAR PHIK 012155 07012KT 3/4SM R06R/4000FT -DZ SCT030 BKN180 27/26 A2992 RMK
VIS S2.
52.
What is the visibility at PAED?
53.
What is the runway visual range at PGUA?
54.
What is the wind at PHIK?
55.
What is the weather at PWAK?
56.
What is the ceiling at PGUA?
57.
Which station is reporting the lowest altimeter setting?
58.
When did PAED experience a frontal passage?
NOTE: Refer to Terminal Aerodrome Forecast (TAF) below to answer questions 58
through 61.
TAF
KMGM 091130Z 091212 25015KT 2SM -RABR SCT002 BKN006 OVC035
FM 2330 27005KT 1/2SM -RAFG SCT002 BKN006 OVC009 PROB30 0002 1/4SM TS
TEMPO 0204 00000KT 1/8SM FG BKN003 BECMG 0406 36010G15KT P6SM SCT012
BKN030.
59.
What is the valid period of this forecast?
E-4
60.
What is the visibility forecast for KMGM at 0500Z?
61.
What is the worst weather forecast for KMGM?
62.
What visibility is forecast for KMGM at 2330Z?
E-5
APPENDIX E
ANSWER SHEET
WEATHER
1.
2.
3.
4
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
high
maritime, continental
Arctic, Polar, Tropical, Equatorial
warmer
heated, unstable
false
true
"k"
"w"
cumuliform
stratiform_________
shower type
light, continuous__
high
low________________
good
poor_______________
gusty
light______________
moderate to severe
none to light______
decrease, increase
true
true
true
false
densities (temperatures)
cold
leading, cold, southeast
ahead, cold fronts
steep, narrow
cumuliform
a. temperature
b. wind
c. pressure tendency
d. moisture
right
warm, northeast
wide, stratiform, ahead
low ceilings, poor visibility, freezing rain, embedded thunderstorms
occluded
stationary
decrease, rise
warm
light
north
warm
cold
cumulus
squall
a. C
b. C
c. R
d. B
e. R
f. R
g. B
false
warmer
leeward
mature
false
55-59 minutes
a. sky clear (0/8)
E-6
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
b. 1/8 to 2/8
c. 3/8 to 4/8
d. 5/8 to 7/8
e. 8/8
lowest, broken, overcast, vertical visibility
true
3/4
11th day at 1555Z
1000 feet AGL
thunderstorms and rain showers
cumulonimbus
2 degrees C
190 degrees at 25 knots, gust 35 knots
2100 meters
not reported
070 at 12 knots
Thunderstorms and heavy rain
vertical visibility 500 feet
PGUA 29.44
FROPA 2100Z
9th day from 1200Z until next day 1200Z
P6SM more than 6 statute miles
TEMPO 0204 1/8 SM, FG, and OVC 003
1/2 SM in light rain and fog
E-7