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Winds & Temperatures Aloft

Introduction:

  • Winds and Temperatures Aloft (FBs) are computer prepared forecasts for specific locations in the contiguous U.S. and a network of locations in Alaska and Hawaii based on the North American Mesoscale (NAM) forecast model run [Figure 1]
  • "FDWinds," now "FBwinds," are produced in both a textual and graphical format
  • This information aids the pilot in:
    • Determining the most favorable altitude based on winds and direction of flight
    • Identifying areas of possible aircraft icing, by noting air temperature of +2°C to -20°C, and temperature inversions
    • Predicting turbulence by observing abrupt changes in wind direction and speed at different altitudes
Winds and Temperatures Aloft Forecast
Winds and Temperatures Aloft Forecast
Wind and Temperature Aloft Forecast (FB) Periods
Wind and Temperature Aloft Forecast (FB) Periods

Issuance & Validity:

Wind and Temperature Aloft Forecast (FB) Periods
Wind and Temperature Aloft Forecast (FB) Periods
Winds and Temperatures Aloft Forecast
Winds and Temperatures Aloft Forecast Header
Winds and Temperatures Aloft Forecast
Winds and Temperatures Aloft Forecast Header

Elements:

  • There are two main elements to a winds and temperatures aloft forecast:
  • Winds and Temperatures Aloft Forecast Altitudes
    Forecast Levels
    Winds and Temperatures Aloft Forecast Altitudes
    Forecast Levels

    Forecasted Data:

    • Issued for a variety of altitudes based on location [Figure 4]
    • "FT" indicates the levels of the wind and temperatures data
    • A four-digit group shows wind direction in tens of degrees, the second two are wind speed in knots
    • Altitudes up to 15,000' the levels are true altitude (references to MSL)
    • Altitudes at or above 18,000' the levels are pressure altitudes (references to FL)
    • The symbolic form of the forecasts is DDff+TT in which:
      • DD is the wind direction
      • ff the wind speed, and
      • TT the temperature
    • Winds:

      • No winds are forecasted within 1,500' of station elevation
      • Winds are forecasted true, indicated in tens of degrees (two digits) with reference to true north and wind speed is given in knots (two digits)
        • 2022: 200@22 knots
      • If forecast speed is less than 5 knots, the coded group is 9900 which means, "light and variable"
        • 990012: winds are light and variable, temperature 12°C
      • If a wind direction is coded between 51 and 86, the wind speed is 100 knots or greater
        • Subtract 50 from the wind and add 100 to the wind
        • 731960:
          • Step 1: 73-50 = 23 or 230
          • Step 2: 19 + 100 = 119
          • Result: 230@119 (temperature 60°C)
      • If the wind speed forecast to be 200 knots or greater, the wind group is coded as 99 knots
        • 189960: 230@200+ (temperature 60°C)
    • Temperatures:

      • No temperatures are forecasted within 2,500' AGL of station elevation
      • No temperatures are forecasted in the 3,000' column
      • A six-digit group includes forecast temperatures in degrees Celsius
        • 192832: the last two digits show 32°C for the temperature but remember above 24,000' the negative sign is excluded
Winds and Temperatures Aloft Forecast Altitudes
Winds and Temperatures Aloft Forecast Data
Winds and Temperatures Aloft Forecast Altitudes
Winds and Temperatures Aloft Forecast Data

Conclusion:

References: