Meteorology
What the exam tests
Meteorology questions cover pressure, temperature, wind, clouds, fronts, icing, thunderstorms, wind shear, altimetry and the interpretation of METAR, TAF, SIGMET and PIREP information.
Core rules
- Pressure decreases with height; altimeter setting errors affect all aircraft in the same area but not terrain clearance.
- Cloud forms when air cools to its dew point by lifting, cooling or mixing; stable air gives stratiform cloud, unstable air gives cumuliform cloud and showers.
- Airframe icing is most likely in supercooled liquid water, often between 0°C and −20°C; freezing rain is especially dangerous.
- Thunderstorms produce gust fronts, microbursts, hail, turbulence and lightning; avoid by a wide margin and do not attempt to fly beneath a storm.
- METAR reports observed conditions; TAF is a forecast with validity, BECMG and TEMPO change groups; SIGMET warns of significant hazardous weather.
Worked example
METAR: “RJTT 121200Z 18012KT 9999 FEW020 SCT040 18/12 Q1012 NOSIG.” Reasoning: day 12 at 1200 UTC; wind 180° at 12 kt; visibility 10 km or more; few cloud at 2,000 ft, scattered at 4,000 ft; temperature 18°C, dew point 12°C; QNH 1012 hPa; no significant change expected. The 6°C spread suggests no low cloud or fog at the reporting time.
Traps
Reading QNH as QFE; confusing BECMG with TEMPO; assuming TAF is observed weather; ignoring the time group; treating a distant thunderstorm as harmless.