METAR and SPECI: Aerodrome Weather Reports and Forecasts

Thirty vocabulary flashcards covering METAR/SPECI structure, wind, visibility, clouds, weather phenomena, and related coding rules.

METAR

Aerodrome routine weather report; issued hourly or every 30 minutes; uses a standard code form.

SPECI

Aerodrome special weather report; issued when specific criteria are met; uses the same code form as METAR and may include a TREND.

TREND

Forecast appended to METAR/SPECI indicating the expected weather change.

IDENTIFICATION GROUPS

Section of METAR/SPECI containing the report type, station ICAO indicator, and observation time; may include COR, NIL, or AUTO.

COR

Code word meaning the report is a correction to a previously transmitted report.

NIL

Code word inserted after the time group to indicate a nil or omitted element in the IDENTIFICATION GROUPS.

AUTO

Indicates the report is from an automated observing system without human intervention.

LUDO

Example ICAO location indicator (e.g., LUDO) used in samples.

SURFACE WIND

Ten‑minute mean wind group; five‑figure, with direction (three digits) and speed (two digits); units KT or MPS.

KT

Knots; unit used for wind speed in METAR/SPECI.

MPS

Metres per second; alternative unit for wind speed.

GUST (G)

G followed by a gust speed (e.g., 31015G27KT); indicates gusts after the mean wind.

WIND VARIATION (V)

Indicates wind direction variation of 60° to less than 180° with mean wind speed; two extreme directions shown with a V between.

VRB

Variable wind; used when wind direction is not fixed (e.g., VRB02KT).

NDV

No Directional Variation; appended to visibility when directional variation cannot be reported.

VISIBILITY GROUP

Prevailing visibility reported in a four‑digit group; if directionally variable, the lowest visibility may be reported.

RVR

Runway Visual Range; R followed by runway designator and / and the RVR in metres; up to four groups.

P2000

Prefix used when RVR exceeds 2,000 m (e.g., R24/P2000).

FEW/SCT/BKN/OVC

Cloud amount abbreviations: FEW (1/8–2/8), SCT (3/8–4/8), BKN (5/8–7/8), OVC (8/8).

CB

Cumulonimbus; significant convective cloud.

TCU

Towering Cumulus; significant convective cloud.

NSC

Nil Significant Cloud; no significant cloud below reporting thresholds.

NCD

No Significant Cloud Detected; cloud not observed by the reporting system.

Cloud base SCT018

Cloud base height encoded with base 1,800 ft (018).

VV (Vertical Visibility)

Vertical visibility when the sky is obscured; encoded as VV followed by value (e.g., VV003).

CAVOK

Ceiling And Visibility OK: 10 km+ visibility, no cloud below 1,500 m (or higher minimum) and no significant weather.

PRESENT WEATHER

Weather phenomena coded with abbreviations (RA, SH, FG, BR, FU, VA, DS, SS, TS, FC, VC) including intensity (+/−) and descriptors.

REUP

Recent unknown precipitation; reported when an automatic system cannot identify the precipitation.

QNH

Pressure – QNH: sea‑level pressure in hectopascals; e.g., Q0995 for 995 hPa.

MISSING ELEMENTS

If an element is temporarily missing or incorrect, it is replaced by a solidus (/) for each missing digit (e.g., ///KT, R24/////).