The basic guidance for use of the TAF code is provided in Naval Oceanography Command instruction (NAVOCEANCOMINST) 3143.1, Terminal Aerodrome Forecast (TAF) Code; NAVAIR 50-1P-11, International Meteorological airfield (in the airfields control zone as defined by the base operations manual) to other users. It may also be used in-house for briefing purposes.

Learning Objective: List five basic guidelines for composing a terminal aerodrome forecast.

GUIDELINES FOR COMPOSING A TERMINAL AERODROME FORECAST

Before we cover the specifics of the code, I want to stress five important rules that you, as the forecaster or briefer, should keep in mind when composing a terminal aerodrome forecast: your forecast should be complete; it should be accurate; it should be specific; it should be on time; and it should be written to cover weather occurrences, not to cover the check blocks on a forecast verification sheet. There are many users who rely on the information contained in the TAF code to make significant judgments and operational decisions. Pilots will either fly or stay grounded based on your forecast. Event planning for the next 24 hours may hinge on your forecast. Many man-hours and Government dollars will be spent either economically or wastefully based on your forecast. Because of this, it is essential that you remember these basic guidelines when writing your forecast.

Be complete! Adequately describe all weather events that you feel will occur in the entire 24-hour period covered by your forecast. The TAF is given wide distribution through both local and limited worldwide electronic dissemina-tion. While the local pilots may find it convenient to pick up the phone and get an update every hour or so, this isnt as easy for the pilot inbound to your station from overseas or for the pilot flying an 18-hour round-robin mission without intermediate stops. When you are writing a TAF, say the 0900Z forecast (which will be valid until 0900Z the following morning), write it as if you know that the person receiving it will not be able to receive an update and will be flying on your forecast at 0830Z the following morning. If you feel fog will develop at 0845Z, include it in the forecast. Do not ignore it just because its near the end of the forecast period. One of the biggest problems we have seen with TAFs (and PLTAFs) is that some forecasters actually write only a 6-hour forecast and assume that the next forecast issued 6 hours later will take care of anyone who will be flying later during the day.  

Be accurate! The forecaster must insure that all available information has been used and properly interpreted when the forecast is made. The forecaster, or the briefer, must also insure that all elements of the forecast are accurately encoded. Proofread the TAF before you transmit. It is just as important to continuously monitor the developing weather conditions so that amendments to the TAF may be issued if necessary.

Be specific! Specify the approximate time any significant changes are expected to begin and end. To say that the prevailing conditions over a 24-hour period will be VFR, with an intermittent IFR condition covering the entire forecast period, is simply an admission by the forecaster that the forecaster really doesnt have the slightest idea what will happen. If, for example, you are writing a forecast for the Tropics and expect fine flying weather except in isolated afternoon or evening rain showers, nail down the time when rain showers will occur within a specific time window. Do not get overly specific, however. Base your change groups only on significant changes in the forecast. The cloud ceiling changing from 12,000 feet to 10,000 feet usually isnt significant. A ceiling changing from MVFR to IFR would be very significant. Some forecasters routinely use change groups at constant times or time intervals  such as at 1500Z forecast with change groups at 1800Z, 0000Z, 0600Z, and 1200Z. These TAFs should be carefully scrutinized prior to use, since it is highly unlikely that the weather conditions will actually change at specified intervals.

Be on time! Start writing the forecast early enough so that it may be encoded and transmitted by the proper file time. All TAFs will have a valid period of 24 hours and will be filed at 6-hour intervals with file times at 0300Z, 0900Z, 1500Z, and 2100Z. If your data transmission terminal is not operational and your file time is approaching, investigate alternative means to transmit your TAF. This may be as simple as calling another NOC Detachment/Facility/Center and dictating your TAF over the phone so that they may transmit it for you.

Write to cover weather occurrences, not the blocks on a verification sheet! While forecast verification programs are helpful in a forecast improvement or a training program, occasionally people place more importance on writing a forecast that will be easier to verify than on writing an accurate forecast. If you concentrate on writing a complete, specific, and accurate forecast, and are doing a good job at it but still receive low verification scores, then talk to your LPO. The problem may not lie with your forecasts, but with the verification criteria. Remember, the primary goal of forecasting is Flying Safety.

Learning Objective: Identify the code groups used in the Terminal Aerodrome Forecast (TAF) code.

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