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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

Issuance & Validity:


Winds and Temperatures Aloft Forecast
Figure 3: Winds and Temperatures Aloft Forecast Header

Elements:


Header:

  • "FD" indicates a Winds and Temperatures Aloft
  • "FD1US1" is a standard line regardless of reported region
  • Data is collected at the date time group (DTG) listed
    • "DATA BASED ON: 121800Z:" Data is based on the 12th day of the month, 1800Z
  • Valid at the "FOR USE" times listed
    • "FOR USE: 2000-0300Z:" for use between 2000Z and 0300Z
  • "TEMPS NEG ABOVE 24000" is a standard line
    • Since temperatures above 24,000' are always negative, the minus sign is omitted

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
  • Winds and Temperatures Aloft Forecast Altitudes
    Figure 4: Forecast Levels
  • 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

Example:

  • The following is a typed out version of the example pictured above
  • Move your mouse over the numbers to show what they mean decoded
  • The numbers in red were changed for the purpose of citing a wider range of examples
  • Additional explanation can be found at AviationWeather.gov

FD1US1
DATA BASED ON 131800Z
VALID 140000Z FOR USE 2000-0300Z. TEMPS NEG ABV 24000
FT 3000 6000 9000 12000 18000 24000 30000 34000 39000
EYW

2022

2028+16

2023+12

2122+06

2027-05

2126-16

212830

232340

233153

JAX

2136

2237+15

2237+10

2239+05

2334-06

2238-15

234130

245141

246153

MIA

2212

2221+16

2019+10

2125+06

2126-05

2227-15

242631

242540

242653

MLB

2221

2133+15

2036+09

2131+05

2239-06

2233-16

243230

243641

244553

PFN

3105

9900+15

3012+09

2514+04

3109-05

2612-17

231833

223743

236453

PIE

2219

2317+16

2218+10

2118+05

2321-05

2321-16

243731

234541

235152

TLH

3212

2822+15

2921+10

2913+06

3016-06

2616-17

252132

234342

246753

ATL

0733

0925+14

0717+09

0714+04

0510-07

0409-18

200934

201544

212654

CSG

0724

0611+14

0412+09

0512+05

3511-07

3312-18

231133

221243

232954

SAV

1730

1829+14

1831+10

1732+05

1930-07

2037-17

223231

244042

255853

HAT

9900

2607+13

2514+09

2616+04

2413-08

2515-19

263234

245143

256556

ILM

1708

1907+14

2214+09

2319+04

2320-08

1920-18

202833

223843

235156

RDU

1309

9900+13

2309+08

2417+04

2314-08

2415-19

242734

234144

235656

CAE

1323

1320+14

1417+09

1513+04

1717-08

1920-18

192832

203043

212956

CHS

1624

1825+14

1926+09

1827+05

1923-07

1928-18

214032

223742

234154

FLO

1418

1315+14

1716+09

1916+04

2017-08

1922-18

203033

213743

224056

GSP

0618

1014+14

1209+09

1408+03

1306-07

9900-19

191934

203444

213456

2XG

1921

2024+15

2028+09

2130+05

2240-06

2237-16

223631

731960

779941


Conclusion:

References: