Terminal Aerodrome Forecast (TAF)

Nov 10, 2017

Terminal Aerodrome Forecast (TAF)

One very useful weather report that pilots use often is a TAF. A TAF is the international standard code format for terminal forecasts issued for airports. TAFs are valid for a 30 hour time period and are issued 4 times a day at 6 hour intervals. The forecast includes forecasted wind speed, wind direction, visibility, ceiling, type of precipitation (i.e. snow, rain, etc.) and/or weather phenomenon.Taz Christman does an excellent job explaining TAFs, as a guest instructor for Helicopter Online Ground School

TAFs complement and use similar encoding to METAR reports. They are produced by a human forecaster based on the ground. For this reason there are considerably fewer TAF locations than there are airports for which METARs are available. TAFs can be more accurate than Numerical Weather Forecasts, since they take into account local, small-scale, geographic effects.

KXYZ 051730Z 0518/0624 31008KT 3SM -SHRA BKN020
FM052300 30006KT 5SM -SHRA OVC030
PROB30 0604/0606 VRB20G35KT 1SM TSRA BKN015CB
FM060600 25010KT 4SM -SHRA OVC050
TEMPO 0608/0611 2SM -SHRA OVC030

The first line contains identification and validity times.

TAF indicates that the following is a terminal aerodrome forecast.
KXYZ indicates the airport to which the forecast applies (ICAO airport code).
051730Z indicates that the report was issued on the 5th of the month at 1730 UTC (also known as Zulu, hence the Z).
0518/0624 indicates that the report is valid from the 5th at 1800 UTC until the 6th at 2400 UTC.
The remainder of the first line contain the initial forecast conditions. Variations of the codes used for various weather conditions are many.[3]

31008KT indicates that the wind will be from 310° true at 8 knots (9 mph; 4 m/s).
3SM -SHRA BKN020 indicates that visibility will be 3 statute miles (5 km) in light (-) showers (SH) of rain (RA), with a broken ceiling (between  5⁄8 and  7⁄8 of the sky covered) at 2,000 feet (600 m) above ground level (AGL).
Each line beginning with FM indicates a rapid change in the weather over a period of less than an hour.

Terminal Aerodrome Forecast (TAF)

FM052300 indicates the next period lasts from (FM) the 5th at 2300 UTC to the 6th at 0600 UTC (the effective time on the next FM line). The remainder of the line has similar formatting to the other forecast lines: 30006KT wind from 300° at 6 knots (11 km/h; 6.9 mph), 5SM visibility 5 statute miles (8 km), -SHRA light rain showers, OVC030 overcast at 3,000 feet (900 m).PROB30 indicates a 30% probability of the following temporary conditions on the 6th between 0400 UTC and 0600 UTC: VRB20G35KT wind of variable direction at 20 knots (35 km/h; 25 mph) with gusts up to 35 knots (65 km/h; 40 mph), 1SM visibility 1 statute mile (1.6 km), TSRA thunderstorms and rain, BKN015CB broken cumulonimbus clouds at 1,500 feet (450 m).
FM060600 indicates that the next period lasts from the 6th at 0600 UTC until 2400 UTC (the end of the forecast period, as there is no following FM): 25010KT wind from 250° at 10 knots (20 km/h; 10 mph), 4SM visibility 4 statute miles (6.5 km), -SHRA light rain showers, OVC050 overcast at 5,000 feet (1,500 m).TEMPO means that these conditions are temporarily replaced between 0800 UTC and 1100 UTC with: 2SM visibility 2 statute miles (3 km), -SHRA light rain showers, OVC030 overcast at 3,000 feet (900 m). (The wind speed remains the same as it is not mentioned.)
The final line is for errata, comments, and remarks.

RMK NXT FCST BY 00Z indicates a remark that the next forecast will be issued by 0000 UTC.

 Terminal Aerodrome Forecast (TAF)

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