TAF is an abbreviation for Terminal Aerodrome Forecast. It is a detailed weather prediction at and around the airport. The major difference between a TAF and a METAR is that TAF gives the weather information of the airport and area around the airport however, a METAR gives weather information for the region only above the airport. TAFs are issued at all the airports and are valid for around 24 hours. TAFs are issued at the following times:
Validity of TAF depends upon many factors, therefore they not only last 24 hours, they can even last for 30 hours or even a few hours from the release.
Decoding of TAF
TAFs are generally listed as following:
A change in weather which is expected to happen at a set time.
A change in weather which is set happen somewhere between 2 times.
The weather will change but not permanently. The change should last maximum for an hour.
Majority of the abbreviations used in a TAF are generally similar to a METAR. Check out the METAR Tutorial in order to learn them if you haven’t yet.
For understanding better, let’s consider an example:
Here AMD stands for Amended. This means that the TAF shown is an edited TAF of PHNL(Honolulu). It is followed by the issuing time and date of the TAF which is 24th of the month at 2023Z (8:23 PM Zulu). It is followed by the weather at the airport at the time of issue. It can be easily broken down using the METAR decoding abbreviations. Here SHRA means that there are showers at the airport.
TEMPO 2420/2424 3SM RA BR BKN020 OVC030:
Referring to the table above, Tempo means temporary followed by the date and time. 2420/2424 means that the weather change will occur on 24th of the month from 2000Z to 2400Z. Followed by the weather in that period of time. Again it can be decoded using METAR abbreviations.
FM250600 11015G25KT P6SM -SHRA SCT025 BKN035:
Again referring the table above, FM stands for From followed by the date and tie of change. This means that weather will definitely change on 25th of the month from 0600Z. It is followed by the changed weather description that can be decoded using METAR abbreviations.
The last line is similar to the 3rd line.
IMPORTANT POINTS TO PONDER UPON
All the time in a TAF are in Zulu. Make sure to change it to the suitable time zone of the airport you are seeking.
In order to decode a TAF easily, make sure to be thorough with the decoding of METAR.
Sometimes there might be an equal to sign (=) at the end of the report. It denoted the end of the TAF report.
Some of the points edited by @Mags885 can be found here!. Check them out as they are really important!