Meteorology for Flight Planning and Altimetry
Core concepts
Flight planning meteorology covers winds aloft, temperature, pressure systems, fronts, turbulence, icing, thunderstorms, and visibility. Altimetry is central: QNH, QFE, QNE, transition altitude, transition level, and the standard pressure setting (1013.25 hPa / 29.92 inHg). Above the transition level, fly at flight levels using standard pressure; below, use QNH. The transition layer is between transition altitude and transition level.
Traps
Common confusions: QNH gives elevation above mean sea level; QFE gives height above the aerodrome reference point; QNE is the standard setting used at flight levels. A high-to-low pressure transition (flying from high to low QNH) causes the true altitude to be lower than indicated - 'high to low, look out below'. Temperature errors: cold air makes the true altitude lower than indicated. Also watch for the difference between transition altitude (fixed) and transition level (variable).
Worked example / rule of thumb
Rule of thumb: 1 hPa ≈ 8 ft near sea level; 1°C ISA deviation ≈ 4 ft per 1,000 ft of altitude. Example: at 5,000 ft, temperature 10°C below ISA → true altitude is about 5,000 − (4×5×10) = 4,800 ft. If QNH is 1003 (below standard 1013), the altimeter reads high relative to true altitude - subtract about (1013−1003)×8 = 80 ft at low level. Always verify the transition level and set standard pressure when climbing through it.