Meteorology: atmosphere, altimetry, systems and reports
The atmosphere
ISA: sea level 15 °C, 1013.25 hPa, lapse rate 1.98 °C per 1 000 ft to 36 090 ft (tropopause), then isothermal to 65 000 ft. Pressure falls roughly 1 hPa per 27 ft near sea level and about 1 hPa per 100 ft near FL180.
Altimetry
QNH gives elevation on the ground; QFE gives height above the reference point; QNE (1013.25) gives flight levels above the transition altitude. Above the transition level, use standard pressure. "High to low, look out below": flying toward lower pressure without resetting the subscale makes true altitude lower than indicated. The same applies flying from warm to cold air - "warm to cold, look out below".
Weather systems
Air masses; fronts (cold: narrow, fast, showery, wind shift; warm: wide, layered, steady precipitation); depressions and their life cycle; troughs, ridges and the jet stream with CAT near the tropopause. Thunderstorms: three stages and hazards (downburst, hail, icing, lightning, tornado). Icing: clear ice (large droplets, supercooled large droplets, 0 to −10 °C), rime (small droplets, −10 to −20 °C), and the factors governing accretion rate.
Worked example
Decode "UAAA 121230Z 24008MPS 9999 BKN030 18/09 Q1015": Almaty, 12th, 12:30 UTC, wind 240° at 8 m/s (8 m/s ≈ 16 kt), visibility 10 km or more, broken cloud at 3 000 ft, temperature 18 °C, dewpoint 9 °C (spread 9 °C), QNH 1015 hPa. Kazakhstan reports wind in metres per second.
Traps
Treating the transition altitude as a fixed worldwide value; confusing QFE with QNH; forgetting that windshear and microbursts are close-in threats.