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Lesson 6.3 – Air Masses, Fronts & Weather Patterns
Large bodies of air with fairly uniform temperature and moisture characteristics are called air masses. When two different air masses meet, they form a front. Most significant weather occurs along fronts.
Reference:
FAA Pilot’s Handbook of Aeronautical Knowledge (PHAK), Chapter 12 – Weather Theory
Air Masses
Air Masses
An air mass is a large body of air that has similar temperature and moisture properties throughout.
Air masses are classified by:
Temperature:
Polar (P) – Cold
Tropical (T) – Warm
Moisture:
Continental (c) – Dry (formed over land)
Maritime (m) – Moist (formed over water)
Common air masses affecting the United States:
cP – Continental Polar (cold and dry)
mP – Maritime Polar (cool and moist)
cT – Continental Tropical (hot and dry)
mT – Maritime Tropical (warm and moist)
Fronts
Fronts
A front is the boundary between two air masses.
Types of Fronts:
1. Cold Front
Cold air advances and displaces warmer air.
Slope is relatively steep.
Weather is often narrow but intense: cumulus clouds, showers, thunderstorms, turbulence, and a rapid temperature drop after passage.
Winds shift sharply (usually from southwest to northwest).
2. Warm Front
Warm air advances over retreating colder air.
Slope is gentle.
Weather is usually widespread and more gradual: stratiform clouds, steady precipitation, poor visibility, and possible fog.
Temperature rises slowly after passage.
3. Stationary Front
Neither air mass is making significant progress.
Weather can be similar to a warm front and may persist for several days.
4. Occluded Front
A cold front catches up to a warm front.
Complex weather that can combine characteristics of both cold and warm fronts.
Typical Weather Sequence
Typical Weather Sequence
Approaching Warm Front:
Lowering ceilings, thickening stratiform clouds, steady precipitation, decreasing visibility.
Approaching Cold Front:
Increasing cumulus development, possible thunderstorms, gusty winds, rapid weather changes as the front passes.
Key Points to Remember
Key Points to Remember
Air masses are classified by temperature (polar/tropical) and moisture (continental/maritime).
Cold fronts usually bring narrow bands of more intense weather.
Warm fronts usually bring widespread, steadier, and longer-lasting weather.
The most significant weather often occurs near fronts.
Knowing the type of front approaching helps you anticipate the kind of flying conditions to expect.
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