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Page Title:
The Forecast Surface Air Temperature Group |
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The Forecast Surface Air Temperature Group 0G1G1T1T1 is the forecast surface air temperature group. It is included only in the sections of the forecast where necessary. Normally it is used to forecast the minimum temperature in the section of the forecast covering the period of time when the minimum temperature is expected to occur, and to forecast the maximum temperature in the portion of the forecast covering the period of time when the maximum tempera-ture is expected to occur. It may be used as often as necessary within the forecast to indicate significant temperatures.0 is the group indicator of the temperature forecast. G1G1 is the valid time, to the closest whole hour, of the temperature forecast.T1T1 digits. Prefix a freezing temperature forecast with an M. For example, 7C forecast to occur at 1015Z is encoded as 010M07.I The Forecast Icing Group 61ch1h1h1tL is the forecast icing group that is used whenever any type of icing condition is forecast outside of thunderstorms (thunderstorms is 10,000 meters or greater; there are no clouds imply moderate or greater icing). Omit the group when no icing is forecast. Use as many groups as necessary to describe all layers of expected icing. 6 is the icing group indicator. Ic is the icing type and intensity code from table 4-4-4. When forecasting icing where either the intensity or the type are borderline conditions, use the higher code figure. h1h1h1 is the height of the base of the icing layer in hundreds of feet above the surface (AGL), rounded down to the lowest hundred. For example, if you forecast an icing layer base at 395 feet, you would encode 003. fL is the thickness of the icing layer in thousands of feet, rounded up to the nearest thousand feet. For example, you forecast moderate mixed icing from 730 feet to 1,800 feet (the layer is actually 1,070 feet thick), you would round up and encode as 2. The group would read 640072. If an icing layer exceeds 9,000 feet in thickness, repeat the entire group using the top of the lower 9,000-foot layer as the base of the next layer. |
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