Meteorological Observations, Reports and Forecasts (METAR, TAF, SIGMET, Charts)
Decoding reports
Know the METAR and TAF formats cold: wind direction and speed with gusts, visibility, runway visual range, present weather, cloud amount and base, temperature and dew point, QNH, and trend or validity. Cloud amounts: FEW (1-2 oktas), SCT (3-4), BKN (5-7), OVC (8). Heights are in feet above aerodrome level. CAVOK means visibility 10 km or more, no cloud below 5000 ft or below the highest minimum sector altitude, and no significant weather. SPECI is a special report issued when conditions change significantly. TREND gives a short-term forecast after the observation.
Forecasts and warnings
A TAF gives a forecast for a defined period. SIGMET warns of significant weather such as thunderstorms, severe turbulence, icing or volcanic ash; AIRMET covers less severe hazards. GAMET is a low-level area forecast. Know which product answers which question, and beware of validity times in UTC and of the difference between TEMPO (temporary fluctuations) and BECMG (gradual permanent change).
Charts
Low-level and significant weather charts show fronts, pressure centres, isobars, jet streams, tropopause height and areas of turbulence, icing and CB. Upper-wind and temperature charts give winds and temperatures at standard levels. The traps are reading the wrong time group, confusing QNH with QFE, and misreading the cloud amount symbol.
Worked example
METAR: 27015G25KT 9999 SCT030 BKN080 18/12 Q1015. Wind 270° at 15 kt gusting 25, visibility 10 km or more, scattered cloud at 3000 ft, broken at 8000 ft, temperature 18°C, dew point 12°C, QNH 1015 hPa. Spread of 6°C suggests a convective base near 2400 ft.