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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
Figure 1: Winds and Temperatures Aloft Forecast
Wind and Temperature Aloft Forecast (FB) Periods
Figure 2: Wind and Temperature Aloft Forecast (FB) Periods

Issuance & Validity:

Wind and Temperature Aloft Forecast (FB) Periods
Figure 2: Wind and Temperature Aloft Forecast (FB) Periods
Winds and Temperatures Aloft Forecast
Figure 3: Winds and Temperatures Aloft Forecast Header
Winds and Temperatures Aloft Forecast
Figure 3: 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
    Figure 4: Forecast Levels
    Winds and Temperatures Aloft Forecast Altitudes
    Figure 4: 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
Figure 5: Winds and Temperatures Aloft Forecast Data
Winds and Temperatures Aloft Forecast Altitudes
Figure 5: Winds and Temperatures Aloft Forecast Data

Conclusion:

References: