Meteorology: Pressure, Stability and Aviation Hazards
What you must know
Meteorology questions cover the atmosphere's structure, pressure and altimetry, temperature, stability, moisture, clouds, precipitation, wind, air masses, fronts, icing, turbulence and thunderstorm avoidance. Understand the standard atmosphere, QNH, QFE and QNE, and how to set and interpret the altimeter. Know that stability depends on the environmental lapse rate versus the adiabatic rates, and how stability determines cloud type and turbulence. Learn the formation of cumulonimbus, the hazards inside and near it, and the rule to avoid by at least 20 nautical miles. Understand wind shear, mountain waves, and the conditions favouring carburettor and airframe icing.
Traps in questions
- Confusing QNH (altitude above mean sea level) with QFE (height above the aerodrome).
- Assuming a high QNH always means good weather; pressure is not visibility.
- Forgetting that temperature and dewpoint close together favour fog and carburettor icing.
- Believing you can safely overfly a cumulonimbus at PPL altitudes - do not.
Worked rule of thumb
Estimate cloud base: spread (temperature minus dewpoint in °C) × 400 ft. Example: temperature 22 °C, dewpoint 16 °C, spread 6 °C, so cumulus bases around 2,400 ft above the surface.
Study approach
Keep a daily weather log: pressure, wind, cloud and visibility, and predict each day before checking.