FAA Flight Instructor Airplane (FIA)Weather and Weather ServicesMedium
A winds aloft forecast (FD) group for the 39,000-foot level reads '751960.' How should a pilot decode this group?
- AWind 025° at 96 knots, temperature -60°C
- BWind 750° at 196 knots, no temperature given
- CWind 250° at 119 knots, temperature -60°C
- DWind 075° at 19 knots, temperature -60°C
Show answer & explanationAnswer & explanation
Correct answer: C. Wind 250° at 119 knots, temperature -60°C
When forecast wind speed at or above 24,000 feet is 100 to 199 knots, 50 is added to the coded direction and 100 is subtracted from the coded speed. Here, direction code 75 minus 50 = 25 (250°), and speed code 19 plus 100 = 119 knots; temperature is -60°C at this altitude.
Why the other options are wrong
- A. This incorrectly swaps and miscalculates the direction and speed digits.
- B. This misapplies the coding rule; direction cannot exceed 360° and the format is misread.
- D. This ignores the required adjustment for high-speed winds at this altitude.
Winds Aloft (FD) Decoding
FD forecasts encode wind direction, speed, and temperature in groups of digits, with special rules for high-speed winds at high altitudes.
- First two digits = wind direction (tens of degrees)
- Next two digits = wind speed in knots
- At or above 24,000 ft, if speed is 100-199 kt, add 50 to direction and subtract 100 from speed
Memory trick: Add 50 to direction, subtract 100 from speed when winds roar past 100 knots up high