Sun Sep 07 2008 09:32 PM
Wind Speeds and Category

Remember, the wind speeds found above the surface. Whether by SFMR, dropsonde or HDOB are nearly Always reduced to the surface by roughly 90%.

100kt flight level wind reduces to roughly 90mph at the surface.

Flight level wind in knots x 1.15 = flight level wind in mph x 0.90 = surface wind estimate. This is for the 700mb or 10000ft flight level. But it is close enough for the lower levels.

Damage difference between a 100mph surface wind and a 140mph surface wind is roughly the difference between loosing your roofing materials to loosing your whole roof and more.

See the enhanced Fujita Scale at http://www.spc.noaa.gov for more information.

Note: This is NOT an official page. It is run by weather hobbyists and should not be used as a replacement for official sources. 
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