Meteorology
Meteorology
Meteorology questions test operational interpretation: what the observation or forecast means for runway choice, approach minima, icing, turbulence and thunderstorm avoidance. You need to decode METAR and TAF groups accurately and translate them into ATC action.
Core rules
- METAR wind is true direction, mean speed, gusts and variation; runway reports and ATIS may use magnetic direction.
- QNH is the pressure setting that makes the altimeter read elevation when on the ground; QFE reads height above a reference point. A falling QNH indicates deteriorating weather.
- Low-visibility procedures are triggered by unit-specific RVR and ceiling criteria; do not apply a single universal threshold.
- Thunderstorms bring wind shear, microbursts, hail and icing; do not vector aircraft through an active cell.
- Temperature/dewpoint spread below 3°C suggests fog or low cloud risk, especially overnight.
Worked example
Decode: EGLL 121250Z 24012KT 210V280 9999 -RA BKN012 12/10 Q1012. Wind is from 240° true at 12 kt, varying between 210° and 280°; visibility 10 km or more; light rain; broken cloud at 1,200 ft; temperature 12°C, dewpoint 10°C; QNH 1012 hPa. The spread is 2°C, so low cloud or mist is plausible. For ATC, the ceiling is 1,200 ft and light rain may reduce braking action; the controller should consider trend information and runway condition.
Traps
Do not read 9999 as 9,999 m; it means 10 km or more. Do not treat BKN as scattered. Do not confuse QNH with QFE when issuing an altitude. Do not use a TAF as an observation; it is a forecast with validity periods.