2016 March 27

Terminal Aerodrome Forecasts (TAFs) are detailed, accurate weather forecasts which describe the expected weather conditions at an airport, usually for a 24 hour period. Amateur astronomers, outdoor enthusiasts, and others can use TAFs to get a good idea of what the weather will be like at a given location. The first step is to find the nearest sizable airport [1] or military airfield. If the area is far away from any aerodromes, select the three or four air facilities so that they form a triangle or square with the area of interest near the center.

Next, look up the four-letter codes for the selected airport(s). A list of selected aerodrome identifiers is listed below.

To find the ID of airports not in the list, click on the following link:

Once you have the air facility ID(s), click on the following link to download the most recent TAF(s):

You'll notice that the TAF(s) are in a coded form. The format is as follows:

Each of the TAF sections are explained in detail below.

This is the four-character identifier of the air facility.

The date and time when the forecast was completed. The first two digits are the day of the month, followed by the time (in UTC). For example, an origin date/ time of

means that the TAF was completed on the 17th at 1155 UTC.

The time period which the TAF covers, usually 24 hours. This consists of a two- digit date followed by a two-digit beginning hour and two-digit ending hour. In the case of an amended forecast, or a forecast which is corrected or delayed, the valid period may be less than 24 hours. Here are some typical entries:

The first three characters is the direction, in degrees from magnetic north, from which the wind will be blowing. The next two characters are the wind speed. Next is KT, the abbreviation for knots. If the wind is gusting, the abbreviation G is present followed by the maximum wind speed of the gusts. Here are some typical wind entries:

This is a measure of how far features can be seen along the ground. U.S. civilian airports express visibility in statute miles; U.S. military facilities express it in meters. The following are some typical horizontal visibility entries:

This is the amount of cloud cover (SKC, FEW, SCT, BKN, or OVC) followed by the height of the clouds given in thousands and hundreds of feet. For example,

means scattered clouds at 500 feet, broken cumulonimbus clouds at 2,500 feet, and broken clouds at 25,000 feet. Cumulonimbus clouds the only cloud types predicted in TAFs. When the sky is obscured by fog or mist, a VV (vertical visibility) is used followed by the vertical visibility in hundreds of feet.

This section contains the contraction WS if wind shear is predicted. The WS is followed by the height of the wind shear in hundreds of feet above ground level, the direction (in degrees from magnetic north) from which the wind is expected to blow, and the predicted wind speed in knots. For example,

translates to wind shear at 1,000 feet with a wind direction of 180 degrees and windspeed of 40 knots.

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