Meteorology
What the exam tests
Meteorology covers the ISA, pressure and altimetry, clouds and icing, thunderstorms and wind shear, METAR/TAF decoding, and Japanese seasonal weather.
Core rules
- ISA sea level: 15°C, 1013.25 hPa; lapse rate about 2°C per 1,000 ft; tropopause near 36,000 ft.
- QNH gives altitude above mean sea level; QFE gives height above the aerodrome; QNE is 1013.25.
- METAR trend groups: BECMG means gradual change, TEMPO temporary fluctuations, NOSIG no significant change.
- Clear ice forms in freezing rain or large supercooled droplets; rime ice in stratiform cloud.
- SIGMET warns of severe turbulence, icing, volcanic ash and tropical cyclones; AIRMET covers moderate hazards.
- In Japan, the baiu front brings heavy rain in June–July, typhoons peak in August–September, and winter monsoon snow affects the Sea of Japan side.
Worked example
QNH 1,000 hPa, altimeter set 1,013 hPa, indicated 5,000 ft. The subscale is 13 hPa high, so the aircraft is about 390 ft lower than indicated: roughly 4,610 ft. Flying from high to low pressure without resetting is the classic 'look out below' error.
Traps
Treating TEMPO as a permanent change; reading cloud height as altitude; and forgetting that wind shear and microbursts can occur without a visible thunderstorm at the runway.