Reference Tool

TAF Decoder

TAF (Terminal Aerodrome Forecast) is a structured forecast of weather conditions at an airport over a defined period (typically 24 or 30 hours). Issued every 6 hours, it is the airport-specific forecast that dispatchers use for flight planning. Structure overlaps with METAR plus dedicated change-group keywords.

Example and Decode

TAF EGLL 211100Z 2112/2218 24015G25KT 9999 SCT030
 BECMG 2118/2120 26020G30KT
 TEMPO 2200/2206 4000 -RA BKN010

TAF EGLLHeathrow forecast
211100Zissued day 21, 11:00 UTC
2112/2218valid from 21 12:00Z to 22 18:00Z (30 hours)
24015G25KT 9999 SCT030initial conditions
BECMG 2118/2120gradual change between 21 18:00Z and 21 20:00Z
TEMPO 2200/2206temporary conditions (total duration less than half the period) between 22 00:00Z and 22 06:00Z
-RAlight rain

Change Group Keywords

BECMG

Gradual change expected over the specified window. Change is permanent for the remainder of the forecast.

TEMPO

Temporary fluctuations lasting less than an hour each and totalling less than half the specified window.

Rapid change at a specific time. Everything that follows replaces the previous forecast.

PROB30 / PROB40

Probability of specified conditions occurring during the window (30% or 40%). Higher probabilities are issued as FM or BECMG.

Educational reference. Operational use requires verified TAF from the issuing authority. See Terms of Service.