Meteorological Information, Reports and Forecasts
Meteorological Information, Reports and Forecasts tests decoding and using METAR, SPECI, TAF, trend forecasts, warnings and in-flight reports.
METAR and SPECI
Routine (METAR) and special (SPECI) reports give: wind in degrees true with speed and gusts, visibility, RVR where applicable, weather, cloud in oktas, temperature/dewpoint and QNH. Cloud amounts: FEW 1–2, SCT 3–4, BKN 5–7, OVC 8 oktas; BKN or OVC gives a ceiling. 9999 means 10 km or more; CAVOK means visibility 10 km or more, no cloud below 5000 ft or the highest minimum sector altitude, and no significant weather.
TAF and trends
A TAF is valid for a stated period; a trend forecast attached to a METAR applies to the following two hours. Change groups: BECMG (gradual change), TEMPO (temporary fluctuations, normally not more than half the period), FM (permanent change), PROB30/PROB40 (probability, not a trend).
Warnings and reports
SIGMET for thunderstorms, volcanic ash, tropical cyclones, severe icing and severe turbulence; GAMET for low-level aviation; AIRMET for moderate hazards; PIREP/AIREP for actual in-flight conditions.
Worked example
27015G27KT 240V310 9999 -SHRA FEW020 BKN035 17/13 Q1012 TEMPO 4000 SHRA BKN012 means: wind from 270° at 15 kt gusting 27 kt, varying between 240° and 310°; visibility 10 km or more; light rain showers; few cloud at 2000 ft, broken at 3500 ft; temperature 17 °C, dewpoint 13 °C; QNH 1012 hPa; temporarily for up to two hours, visibility 4000 m in moderate rain showers with broken cloud at 1200 ft.
Traps
- Reading 9999 as a numeric code rather than 10 km or more.
- Treating PROB30 as a TEMPO.
- Forgetting that METAR and TAF winds are true while ATIS and ATC winds are magnetic.
- Confusing BECMG with FM.