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APPENDIX D
FRONTAL WEATHER
STUDENT HANDOUT
TERMINAL LEARNING OBJECTIVE (TLO): At the completion of this lesson, the student will:
ACTION: Plan a flight mission IFR or VFR in accordance with weather conditions stated in FM 1-230 and
AR 95-1.
CONDITION: In a classroom environment.
STANDARD: IAW FM 1-230.
A. ENABLING LEARNING OBJECTIVE (ELO) #1:
ACTION: The student will identify the characteristics common to all fronts.
CONDITION: In a classroom environment and given a student handout.
STANDARD: IAW FM 1-230.
a. Definition of a front- A boundary between air masses of different densities.
b. Frontal formation--when two high pressure cells exist so that the circulation of air is converging
between them, a front is formed. Due to circulation around these cells, the warmer air from one cell is
meeting colder air from the other. The converging air currents veer upward creating a zone of low
pressure. This is a front.
c. Cause of frontal weather--the primary cause of frontal weather is the lifting of warm moist air by more
dense air. Therefore, all fronts have a temperature inversion.
d. Frontal discontinuities.
(1) Temperature.
(2) Moisture content (dew point).
(3) Pressure.
(4) Wind shift.
NOTE: Primary factors affecting frontal weather are: slope and speed, moisture content and stability.
B. ENABLING LEARNING OBJECTIVE (ELO) #2:
ACTION: Identify the general characteristics of a cold front.
CONDITION: In a classroom environment and given a student handout.
STANDARD: IAW FM 1-230.
a. Cold front--the leading edge of a cold air mass normally
moving from northwest to southeast.
b . Vertical cross-section
c. Slope - 1:50 to 1: 100 (avg 1:80)
d. Clouds - cumuliform predominant
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e. Weather
(1) Type – post-frontal, can be violent.
(2) Coverage – critical area is on average, 50-miles wide.
(3) Winds – generally from the NW behind the front, from the SW ahead of the front.
(4) Movement – to the SE.
(5) Speed – average 25 kts. If moving faster than 25 kts, a squall line may form as much as 300
miles ahead. Squall lines may include tornadoes, hail and destructive winds.
f. Weather chart portrayal
(1) Sectional (local) blue line
(2) Graphic depiction
C. ENABLING LEARNING OBJECTIVE (ELO) #3:
ACTION: Identify the general characteristics of a warm front.
CONDITION: In a classroom.
STANDARD: IAW FM 1-230.
a. Warm front--the trailing edge of a cold air mass moving
generally to the northeast, being overridden by warmer air.
b. Vertical cross section
c. Slope - average 1:200
d. Clouds - stratiform predominant
e. Weather (1) Type – low ceilings, poor visibility, rain, drizzle, fog, scattered thunderstorms in unstable type,
possible clear ice and/or freezing rain below inversion level.
(2) Coverage – wide spread, 400-600 miles ahead of surface position- prefrontal.
(3) Winds – generally from SW behind and SE ahead of front.
(4) Movement – to the NE.
(5) Speed – average 15 kts.
f. Weather chart portrayal
(1) Sectional (local) red line
(2) Graphic depiction
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D. ENABLING LEARNING OBJECTIVE (ELO) #4:
ACTION: Identify the general characteristics of a stationary front.
CONDITION: In a classroom.
STANDARD: IAW FM 1-230.
a. Stationary front--a front which is not moving. Normally considered stationary with a speed of zero
to less than 5 knots.
b. Slope - similar to a warm front
c. Clouds - warm front type predominant
d. Weather
(1) Type – similar to a warm front
(2) Coverage – large area similar to a warm front
(3) Winds – except in areas of showers, winds are light and variable, but generally tend to
parallel the front in opposite directions.
(4) Movement - unpredictable
(5) Speed – 0 to 5 knots
e. Weather chart portrayal
(1) Sectional (local) - alternating red and blue line.
(2) Graphic depiction
E. ENABLING LEARNING OBJECTIVE (ELO) #5:
ACTION: Identify the characteristics of an open wave.
CONDITION: In a classroom.
STANDARD: IAW FM 1-230.
a. Open wave--wave-like appearance on the
weather map with one portion a cold front and the other
a warm front with an open area in between.
b. Vertical cross section
c. Formation - most often forms from a stationary
front. However it may form from any existing front.
d. Weather - cold front weather associated with the cold front and warm front weather associated
with the warm front, with warm air in the open area between the two fronts. Winds in the open area are
generally southwest.
e. Movement – travels in an easterly direction along the line of the original front from which it
formed.
f. Weather chart portrayal.
(1) Sectional - blue and red line indicating each front and a
wave-like structure.
(2) Graphic depiction
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F. ENABLING LEARNING OBJECTIVE (ELO) #6:
ACTION: Identify the general characteristics of an occluded front.
CONDITION: In a classroom.
STANDARD: IAW FM 1-230.
a. Occluded front - the result of a faster moving cold front overtaking a slower moving warm front. The
effect is one front on top of the other squeezing warm air between.
b. Type--there are two types of this front. They are cold front occlusions and warm front occlusions.
(1) Cold front occlusion--When the cold front runs underneath the warm front, it is called a coldtype occlusion. In this area the coldest, or more dense air, is behind the cold front. The warm or less
dense air of the warm front is lifted aloft and blocked from the surface.
(2) Warm front occlusion--When the cold front runs over the warm front, it is called a warm-type
occlusion. In this area the coldest, or more dense air, is ahead of the warm front. The warm or less
dense air of the cold front is lifted aloft and blocked from the surface.
c. Formation--Since cold fronts move faster than warm fronts, quite often the cold portion of an open
wave will overtake the warm front portion. Depending on the relative densities, the cold front either runs
underneath or over the warm front. The warm air sector is blocked away from the surface and one of the
fronts is lifted aloft forming an occluded front.
d. Vertical cross section.
e. Clouds--both warm and cold front types - stratiform and cumuliform.
f. Weather-- The weather associated with each of these fronts combines the widespread low ceiling
and poor visibilities of the warm front with the severe weather of the cold front. The most severe weather
occurs in the early stages of the occlusion. The warm moist air is being lifted by both the cold front and
warm front and by the squeezing action between them.
g. Winds-- The winds ahead of an occlusion may vary from south to east, but are generally from the
southeast. The winds behind an occluded front will generally be from the northwest.
h. Movement--similar to an open wave – movement to the east.
i. Weather chart portrayal.
(1) Sectional (local)--purple.
(2) Graphic depiction
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NOTE: Difference between the two fronts: From a pilot’s viewpoint, there is very little difference. The
extent of cloud coverage, type of clouds, and severity of thunderstorms are essentially the same. There
is one primary difference, and that is the relative position of the major thunderstorms and severe weather
with respect to the surface position of the occluded front. In the cold-type occlusion, the most severe
weather is more or less centered above occlusion. In the warm type, the most severe weather occurs
ahead of the occlusion.
G. ENABLING LEARNING OBJECTIVE (ELO) #7:
ACTION: The student will identify the proper flight procedures to use when dealing with frontal weather
while conducting flight operations.
CONDITION: In a classroom environment and given a student handout.
STANDARD: IAW FM 1-230.
a. Recognition of type. Each type front presents certain general as well as specific problems to the
aviator. The aviator must learn to recognize the type and intensity of each front in order to analyze its
possibilities without weather maps, and in flight, you must be able to analyze the type front and your
relative position to it from wind direction and clouds.
b. Flight considerations for each type frontal situation.
(1) Cold fronts and squall lines-- Intense cold fronts and squall lines will be more thoroughly
discussed during a later period on weather hazards; however, the general recommendation is “Don’t go!”
When approaching a squall line or other band of severe weather in flight, the best option is to land and
wait for the weather to pass.
(2) Warm fronts--general problems are low ceilings and poor visibilities covering large areas and ice.
(Icing will be covered during a later period on weather hazards.) Fly below freezing levels. Ensure
sufficient fuel for a long instrument flight and possible diversion to an alternate airfield.
(3) Stationary front--general recommendation is the same as for a warm front; however, you should
be alert for the possibility of an open wave and occluded front formation.
(4) Open wave-- It is recommended you avoid the crest of the wave and the cold front portion if
possible. Analyze speed and direction of travel from weather maps and forecasts, as well as observing
turbulence, clouds, and winds during flight. Otherwise, use cold front procedures for the cold portion and
warm front procedures for the warm portion.
(5) Occluded fronts--WARNING!! The occluded front presents the worst possible weather. It
contains the worst of both the cold and warm fronts. Avoid the apex or point of occlusion (junction of the
three fronts) by at least 50 to 100 miles. You can take advantage of tailwinds by circumnavigating to the
right, and at the same time avoid the worst weather. Do not fly through an occluded front; wait,
circumnavigate, or fly through the warm or stationary front separately.
H. ENABLING LEARNING OBJECTIVE (ELO) #8:
ACTION: The student will identify the indications of frontal passage.
CONDITION: In a classroom environment and given a student handout.
STANDARD: IAW FM 1-230.
a. On the ground, frontal passage is easy to recognize. There will be a pronounced wind shift and
change in air temperature. If available, you would also note a change in dew point and barometric
pressure.
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b. In flight, penetration of the frontal plane is more difficult to recognize. The changes are essentially
the same; however, the pressure change may be interpreted as an altitude loss or gain and not
recognized for what it is. Wind changes are difficult to recognize while in flight. The best indicator for the
pilot in flight is the outside temperature gauge. Penetration of the frontal plane is immediately noticeable
by a change in the temperature.
c. Drift correction. Regardless of the type front penetrated, as soon as you note a change in free-air
temperature, anticipate a drift correction to the right. There is one possible exception; the penetration of
the warm frontal plane aloft ahead of an occlusion. However, if you are in that position, drift correction is
one of your minor problems.
NOTE: If possible, avoid flying through an active front. If you must go, penetrate the front at a 90-degree
angle, use proper penetration speed, and maintain a constant attitude.
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