Meteorological Observations: METAR, SPECI, PIREP, and Upper-Air Data
What to decode
Be fluent in METAR and SPECI syntax: station identifier, time, wind (direction, speed, gusts, variability), visibility, runway visual range, present weather, sky condition, temperature/dew point, altimeter, and remarks. Know SPECI is issued for significant changes between routine reports. Understand PIREP content: location, time, flight level, aircraft type, and phenomena such as turbulence, icing, and sky condition. Know upper-air data sources: radiosondes (RAOB), winds and temperatures aloft (FD), and pressure-level charts.
Traps
Questions often confuse statute miles with metres in visibility, or misread wind gusts. Another trap is treating a missing ceiling as unlimited, or misinterpreting RVR as prevailing visibility. Watch for the difference between A01 and A02 remarks, and between true and magnetic wind in reports.
Worked example
METAR CYVR 121800Z 27015G25KT 15SM SCT020 BKN040 12/08 A2992. Wind 270° at 15 kt gusting 25; visibility 15 statute miles; scattered at 2000 ft, broken at 4000 ft (ceiling 4000 ft); temperature 12 °C, dew point 8 °C; altimeter 29.92 inHg.