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TAF

TAF stands for Terminal Aerodrome Forecast and is a weather forecast for an airport with regard to certain parameters that will change during the forecast period. It contains all meteorological information that is important for flight operations. The validity period of the TAFs varies between 9, 12, 18 or 24 hours depending on the airport and is completely reissued at regular intervals. The syntax of the TAF is largely the same as the METAR.

We use the following example for further explanations:

EDDF 041100Z 0412/0518 22020G35KT 9999 SCT040 
TEMPO 0412/0416 22030G40KT SHRA BKN030CB 
BECMG 0418/0420 22015G25KT 
TEMPO 0510/0518 26020G35KT SHRA BKN030CB 
PROB30 TEMPO 0512/0518 TSRA

Base status

A TAF always starts with the base status. This always includes the surface wind, prevailing horizontal visibility, significant weather and cloud cover. Next to the location identifier and the time when the TAF was created is the validity period. In this case, this TAF is valid from the 4th of the month at 12z until the next day at 18z.

EDDF 041100Z 0412/0518 22020G35KT 9999 SCT040 
TEMPO 0412/0416 22030G40KT SHRA BKN030CB 
BECMG 0418/0420 22015G25KT 
TEMPO 0510/0518 26020G35KT SHRA BKN030CB 
PROB30 TEMPO 0512/0518 TSRA

Ideally, the basic status of the TAF at the start of the validity period corresponds to the current METAR at that time.

Change groups

The change groups indicate how the weather will change over the forecast period. Only significant changes to the basic status or the previous change group are taken into account if defined threshold values are exceeded or not reached. The coding again corresponds to METAR coding.

EDDF 041100Z 0412/0518 22020G35KT 9999 SCT040 
TEMPO 0412/0416 22030G40KT SHRA BKN030CB 
BECMG 0418/0420 22015G25KT 
TEMPO 0510/0518 26020G35KT SHRA BKN030CB 
PROB30 TEMPO 0512/0518 TSRA

TEMPO
One or more weather parameters fluctuate significantly within the specified period and each fluctuation lasts no longer than half the period to which the TEMPO group refers.

BECMG
A change in weather starts at the beginning of the BECMG period and is completed by the end of the BECMG period. After the change period, the weather of the BECMG group is a new base status.

PROB
Probability of temporary fluctuation (30% or 40%), only when used with TEMPO. Smaller probabilities are not listed, larger ones are described with BECMG or TEMPO.

FM
Change from a certain point in time.

Further information

The German Weather Service (DWD, Deutscher Wetterdienst) offers a helpful document for decoding METAR and TAF.

Old METARs, TAFs and SPECIs are available at OGIMET.

Processing of current METARs and TAFs at metar-taf.com

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