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ATPL Meteorology (050) study materials
ATPL Meteorology (050) study resources

ATPL Meteorology (050): Meteorological Information: METAR, TAF, SIGMET and Charts

ATPL Meteorology (050) · Work through your exam, one topic at a time.

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Meteorological Information: METAR, TAF, SIGMET and Charts

This domain tests decoding and interpreting coded reports and forecasts, knowing which product covers which phenomenon, and reading the standard charts. Expect a decode question and one on the correct product to consult.

METAR and SPECI

  • Routine aerodrome report, issued typically every 30 or 60 minutes; SPECI is issued on significant change; COR indicates a correction.
  • Order: report type, station, date/time in UTC, wind (direction in degrees true, speed in knots, gusts with G, variable with VRB or a 210V270 range), visibility in metres (9999 = 10 km or more), RVR, present weather (intensity, descriptor, precipitation, obscuration), cloud (FEW, SCT, BKN, OVC with base in hundreds of feet above ground), temperature and dew point, QNH in hPa, then trend.
  • CAVOK means visibility 10 km or more, no cloud below 5,000 ft or below the minimum sector altitude, no cumulonimbus or towering cumulus, and no significant weather.
  • Trend groups: NOSIG, BECMG, TEMPO, valid for the following two hours at the reporting aerodrome.

TAF

  • Aerodrome forecast, usually valid 9-24 hours, with BECMG (gradual change), TEMPO (temporary fluctuations) and FM (rapid change) groups, and PROB30/PROB40 for low-probability conditions.

Warnings and advisories

  • SIGMET: significant meteorological information affecting all aircraft - severe turbulence, severe icing, severe mountain wave, thunderstorms, volcanic ash, tropical cyclone, radioactive cloud, severe dust or sandstorm. Volcanic ash SIGMETs are the exception to the usual short validity.
  • AIRMET and GAMET: information for lower-level operations and light aircraft, covering moderate icing or turbulence, mountain obscuration and low-level phenomena.
  • PIREP/AIREP: pilot reports, urgent or routine, the only direct confirmation of turbulence or icing aloft.

Charts and NOTAMs

  • Surface analysis: isobars typically at 4 hPa, fronts, pressure centres and tendency.
  • Upper-air charts, for example 500 hPa: contour heights, temperature and wind, showing troughs and ridges aloft.
  • Significant weather (SIGWX) charts: Cb, turbulence, icing, jet streams and tropopause height for a stated level band.
  • Wind and temperature aloft charts for flight planning.
  • NOTAMs are operational notices, not meteorological, but often carry airfield weather-related restrictions such as closed runways or inoperative lighting.

Worked example

Decode: METAR EGGW 121150Z 24015G27KT 210V270 9999 -RA BKN012 12/10 Q1005 TEMPO 4000 RA BKN008. Wind 240° true, 15 kt gusting 27, varying 210-270; visibility 10 km or more; light rain; broken cloud at 1,200 ft; temperature 12°C, dew point 10°C - a 2°C spread consistent with the low cloud base; QNH 1005 hPa; temporarily, visibility 4,000 m in moderate rain with broken cloud at 800 ft.

Traps that cost marks

  • Reading METAR wind as magnetic; local reports from ATC may be magnetic.
  • Treating 9999 as unlimited or as 9,999 m rather than 10 km or more.
  • Confusing BKN and SCT, or omitting that cloud bases are above ground.
  • Using AIRMET where SIGMET is required, or quoting CAVOK when a Cb is present.