Meteorological Observations, Reports, Forecasts and Charts
Observations and reports
- METAR: routine aerodrome report (wind, visibility, cloud, temp/dew point, QNH).
- SPECI: special report on significant change.
- TAF: aerodrome forecast, typically 9–24 hours.
- SIGMET: significant en-route weather (thunderstorms, severe turbulence, icing).
- AIRMET: less severe en-route advisories.
Decoding
Wind is given in degrees true and knots (e.g., 27015KT). Visibility in metres. Cloud in oktas (FEW 1–2, SCT 3–4, BKN 5–7, OVC 8). Temperature/dew point in °C. QNH in hPa. Trend groups (NOSIG, BECMG, TEMPO) describe expected change.
Charts
- Surface analysis: isobars, fronts, pressure centres.
- Upper-air charts: 500 hPa etc., showing winds and heights.
- Significant weather (SIGWX) charts: fronts, CB, turbulence, icing.
Worked example
METAR: "EGLL 121150Z 27015KT 9999 SCT025 BKN040 15/10 Q1015 NOSIG." Wind 270° at 15 kt, visibility ≥10 km, scattered cloud at 2500 ft, broken at 4000 ft, temp 15 °C, dew point 10 °C, QNH 1015 hPa, no significant change expected.
Traps
Wind direction in METAR is true, not magnetic. 9999 means 10 km or more. BKN = 5–7 oktas. NOSIG means no significant change within the trend period.