Weather Theory for Pilots: Fronts, Stability, Clouds and Hazards

What you'll learn: why weather happens and which hazards matter for small airplanes. Source: FAA Aviation Weather Handbook, PHAK Ch. 12–13.

Pressure and wind

Air flows from high to low pressure, turned by the Coriolis effect: clockwise around highs and counterclockwise around lows in the northern hemisphere.

Stable vs unstable air

Stable	Unstable
Stratiform clouds, smooth air, poor visibility (haze, fog)	Cumuliform clouds, turbulence, good visibility outside showers

Fronts

Cold front: fast-moving, often narrow band of storms and gusty winds, then clearing.
Warm front: slower, wide area of low clouds, rain and poor visibility.
Look for a wind shift and pressure change when a front passes.

Thunderstorms

Need moisture, unstable air and a lifting action. Stages: cumulus (updrafts), mature (rain begins, worst turbulence), dissipating (downdrafts). Avoid by at least 20 nm when severe.

Icing and fog

Structural icing needs visible moisture and temperatures near or below freezing.
Radiation fog: clear, calm nights. Advection fog: moist air moving over a cooler surface.

Products

METAR (observation; see how to read a METAR) and TAF (forecast, ~5 sm radius).
AIRMET (Sierra: IFR/mountain obscuration, Tango: turbulence, Zulu: icing) and SIGMET/Convective SIGMET.
PIREPs: real reports from pilots.

Check yourself

2 questions. Pick an answer to see why it's right or wrong.