Meteorology for IFR Operations
What IFR pilots must read
IFR meteorology focuses on the phenomena that change approach and departure decisions: low cloud, fog, frontal systems, thunderstorms, icing, turbulence, wind shear, and volcanic ash. Candidates must interpret METAR, TAF, SPECI, SIGMET, AIRMET, and trend forecasts, and must know the difference between forecast and reported conditions. They should also understand pressure systems, the standard atmosphere, and how temperature affects altimetry.
Altimetry and temperature error
Cold temperatures cause the altimeter to over-read, so the aircraft is lower than indicated. The rule of thumb: apply a cold-temperature correction when the aerodrome temperature is below about 0 °C, and never allow the corrected minimum to fall below the published procedure minimum. QNH is set when flying below the transition altitude; standard pressure (1013.25 hPa) above it. The trap is using QFE or QNH in the wrong layer, or forgetting that the transition level varies with pressure.
Icing and turbulence
Know the conditions for airframe icing (visible moisture and temperatures near or below 0 °C) and the categories (trace, light, moderate, severe). For turbulence, know that low-level wind shear is most likely with strong surface winds, frontal passage, or inversions, and that a microburst produces a sudden headwind increase followed by a downdraft and tailwind.
Worked rule of thumb
When a TAF shows TEMPO or BECMG groups, decide whether the change overlaps the planned arrival window. A TEMPO group means temporary fluctuations; a BECMG group means a permanent change within the stated period. Many exam questions hinge on that distinction.
Study approach
Practice decoding a full METAR and TAF line by line, then ask: does this affect alternate selection, approach minima, or fuel?