Using the same Forecast Winds and Temperatures Aloft (FD) from the previous question, note that the temperature is forecast to be +9 degrees Celsius at 6000 feet, +5 at 9000 feet and 01 at 12,000 feet. Above what altitude are all temperatures considered negative in Winds Aloft Forecasts?


15,000 feet


18,000 feet


21,000 feet


24,000 feet

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