TAFs and winds aloft forecasts
9 min readLesson 43 of 59
By the end of this lesson you'll be able to:
- Decode a TAF and its change groups
- Read a winds and temperatures aloft forecast
- Know the time and area each forecast covers
Terminal Aerodrome Forecast (TAF)
A TAF forecasts the weather within 5 statute miles of an airport. TAFs are issued four times a day (0000Z, 0600Z, 1200Z and 1800Z) and are usually valid for 24 or 30 hours.
TAF KSLC 171720Z 1718/1824 33010KT P6SM FEW060 FM172200 30015G25KT P6SM SCT080 TEMPO 1800/1803 4SM -SHRA BKN050 PROB30 1803/1806 VRB20G35KT 3SM TSRA BKN040CB
- 1718/1824: valid from the 17th at 1800Z to the 18th at 2400Z.
- P6SM: visibility greater than 6 statute miles.
- FM172200: "from" the 17th at 2200Z, a rapid and lasting change to these conditions.
- TEMPO: temporary fluctuations lasting less than an hour at a time and less than half the period.
- PROB30: a 30% chance of the conditions in that period (PROB40 is 40%).
- BECMG: a gradual change over the period given.
Winds and temperatures aloft (FB)
The winds aloft forecast gives wind direction (true), speed in knots and temperature in °C at standard altitudes.
- 2714 = wind from 270° at 14 knots, no temperature (temperatures aren't given at 3,000 ft).
- 2725+05 = 270° at 25 knots, +5°C.
- 9900 = light and variable (less than 5 knots).
- If the first two digits are 51 to 86, the wind is 100 knots or more: subtract 50 from the direction and add 100 to the speed. 7325 = 230° at 125 knots.
No winds are forecast for a level within 1,500 feet of the station's elevation. Above 24,000 feet, temperatures are negative and the minus sign is left off.
Key takeaways
- TAFs cover 5 SM around the airport, usually for 24 or 30 hours.
- FM = lasting change, TEMPO = brief, PROB30/40 = chance, BECMG = gradual.
- Winds aloft are true; 9900 = light and variable; 51-86 = add 100 kt.
What the examiner may ask
Practice answering out loud before you open each answer.
How far from the airport does a TAF apply?
Within 5 statute miles of the center of the runway complex.
What does TEMPO mean?
Temporary fluctuations lasting less than an hour at a time and covering less than half of the time period.
How do you pick a cruising altitude using winds aloft?
Compare winds and temperatures at the legal cruising altitudes for your direction, considering terrain, airspace, cloud clearance and groundspeed.
Common mistakes
- Treating PROB30 thunderstorms as 'probably fine'.
- Forgetting winds aloft directions are true.
- Using the 3,000 ft winds at a high-elevation airport where they aren't forecast.
Read it in the FAA sources
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Lesson check
Get every question right to complete the lesson. Take your time; wrong answers explain why.
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