THE TAF CODE FORMAT  

The TAF code format used by the Navy, Marine Corps, and Air Force (the Air Force forecasts for the Army) is the World Meteorologi-cal Organization (WMO) code FM51-V TAF-Aerodrome ¹. The following TAF format is the U.S. Military version currently in use:

The meaning of each group is explained in the following sections.

TAF CCCC (or CCC) G1G1G2G2 and, if required COR and/or AMD is the Message Heading.

TAF is the message identifier and is always sent as the first group when you are transmitting a TAF. This identifier is deleted from individual reports when they are retransmitted in a group (collective), because it will be placed at the beginning of the message containing the group of reports.

CCCC or CCC is the station identifier, a three- or four-letter or letter/numeral combina-tion. Nearly all stations within the continental U.S. use the CCC, a three-letter/numeral the four-letter ICAO identifier in the CCCC

1 A major change is currently in the planning stage for WMO code FM15-V MA TAR and code FM16-V SPECI, which format

2 . U.S. naval ships normally use their four-Ietter International Radio Call Sign (IRCS) for CCCC. IRCSs may be decoded using Call Sign  

G₁G₁G₂G₂ is the valid period of the forecast is the time, in whole hours UTC, of the beginning of the 24-hour valid period of the forecast, or in the case of an amendment, correction, or retarded forecast, the time, to the nearest whole hour, that the change is sent. G₂G₂ the forecast period.

COR is encoded following the valid period of the forecast when any element of the forecast has been corrected. A correction is sent only when the TAF has already been transmitted and it is discovered that some element has been encoded incorrectly or was omitted from the TAF. When a COR is transmitted, the should be altered to reflect the time in whole hours UTC nearest the transmission time. For example, if a correction of the 1515 Pensacola TAF is transmitted at 1530, the header would read TAF NPA 1615 COR. When a correction is transmitted, a COR GGgg group must also be added as the last group in the message. The GGgg reflects the time that the UTC.

AMD will follow the valid period when the forecaster issues an amendment to the forecast. An amendment means that the forecaster has re-evaluated the data and decided to change any element or add a group. When an amendment is issued, the header for an amendment to Pensacolas 1515 TAF transmitted at 1529 UTC would read TAF AMD GGgg, where GGgg is the time is issued.

2 One of the proposed changes in WMO code FM15-V and FM 16-V requires all stations to identify their observations with a four-letter identifier. U.S. stations using a combined letter/numeral (alphanumeric) identifier will have to be reassigned a new identifier. These four-letter identifiers will most likely be used to identify TAFs, as well as observations. An amended TAF should be issued anytime the forecaster considers it advisable in the interest of flying safety or for the efficiency of aircraft operations, flight planning, operational control, and in-flight assistance to aircraft. The forecaster has both the authority and the responsibility to issue amendments, and must determine when amendments should be issued. The forecaster should consider the following guidelines as the minimum criteria for issuing an amendment. These criteria are based on NATOPS require-ments and regulations:

1. When ceilings and/or disabilities are observed or are later forecast to increase to, exceed, or decrease to less than any of the follow-ing values, an amendment should be issued: Ceiling Visibility

2. When expected or actual wind speeds change by 10 knots or more from the forecast speed or when the wind direction changes or is expected to change by 30 degrees or more from the forecast direction when the average wind speed or gusts exceed 15 knots, an amendment must be issued.

3. When thunderstorms were not forecast but later occur or are expected to occur, or were forecast but later are expected not to occur, an amendment must be issued.

4. When precipitation that will affect flying safety (including runway breaking action) was not forecast but occurs or is expected to occur, or was forecast but later is expected not to occur, an amendment must be issued.

5. When the actual or expected altimeter setting will be lower than the minimum altimeter setting forecast (QNH), an amendment must be issued.

RTD is encoded following the valid period when a TAF is transmitted at any time following the scheduled file time. This would be used when the original TAF is transmitted late, or if the original forecast is retransmitted for any reason. Occasionally, the COMEDS, PACMEDS, EURMEDS, or CARMEDS system operator sends a message to all connected terminals that the system has had a failure, and states what data has been lost. If you suspect your TAF was lost in a systems failure, it should be retransmitted as a retarded TAF. In either case, the header would read the same. As an example, we will use a late 1515 TAF from Pensacola, which would read TAF NPA 1515 RTD.

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