BoM TAF Decoder
Paste an Australian TAF or type a Y-code. Metric units and change groups decoded.
Accepts any Australian or international TAF, an ICAO code like YSSY, or an airport name.
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What changes in an Australian TAF
The change groups are the same ones used everywhere: FM, TEMPO, BECMG and the PROB groups. The valid period uses the same four-digit day and hour form on each side.
The units differ from a US forecast. Visibility is in metres, so 9999 means ten kilometres or more, and pressure is QNH in hectopascals rather than inches of mercury.
Australian aerodrome codes all begin with Y. YSSY is Sydney, YMML is Melbourne, YBBN is Brisbane and YPPH is Perth.
TAF3 and the validity periods
The Bureau of Meteorology issues most aerodrome forecasts in the TAF3 format, which means the forecast is divided into periods with defined confidence rather than a single running narrative.
Validity varies by aerodrome. Major fields get 24 or 30 hours, while smaller ones get shorter periods. Read the valid period in the header rather than assuming, because a forecast that ends before your arrival is no forecast at all.
Amendments work the same way as anywhere else. An amended forecast replaces the previous one completely for the rest of the period, and the period shortens rather than restarting. The AMD against COR comparison covers the difference between an amendment and a correction.
TTF: the trend type forecast
Some Australian aerodromes issue a TTF, a trend type forecast appended to the routine observation. It covers the next three hours and, where it exists, it takes the place of the TAF for that window.
That is worth knowing because it changes which product you should be reading. If a field publishes a TTF and you are arriving within three hours, the TTF is the more current statement about the aerodrome.
A TTF uses the same FM, BECMG and TEMPO vocabulary, so nothing new has to be learned to read one.
Reading the result
Find your arrival time first, then read the block that covers it. That block is the prevailing forecast for your hour, and anything layered over it modifies the answer without replacing it.
A TEMPO period is the one that catches people. It does not replace the conditions around it, so both the prevailing and the temporary conditions matter, and the temporary set is the one an alternate has to clear.
For the codes themselves, the TAF abbreviations list covers the forecast-only vocabulary and the international format guide covers what changes outside the United States.
Frequently asked questions
Does this decode Australian BoM TAFs?
Yes. Metric visibility, hectopascal QNH, the standard FM, TEMPO, BECMG and PROB change groups and the Y-prefixed aerodrome codes are all handled by the same engine that reads US forecasts.
What is TAF3?
The Bureau of Meteorology format in which most Australian aerodrome forecasts are issued. It divides the forecast into periods with defined confidence rather than one running narrative, and it decodes with the standard change groups.
What is a TTF?
A trend type forecast appended to a routine observation at some aerodromes, covering the next three hours. Where one exists it supersedes the TAF for that window, so it is the more current statement.
Why do Australian airport codes start with Y?
The Y prefix is the ICAO region code for Australia, the same way K covers the contiguous United States and EG covers the United Kingdom. YSSY is Sydney and YMML is Melbourne.
How long is an Australian TAF valid?
It varies by aerodrome. Major fields get 24 or 30 hours and smaller ones get shorter periods, so read the valid period in the header rather than assuming a standard length.