September 1, 2014

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The Enhanced Fujita Scale for tornado damage was implemented
in the U.S. on Feb. 1, 2007.  Below is a chart that compares the new scale
to the old Fujita Scale.































































FUJITA SCALE DERIVED EF SCALE OPERATIONAL EF SCALE
F Number Fastest 1/4-mile (mph) 3 Second Gust (mph) EF Number 3 Second Gust (mph) EF Number 3 Second Gust (mph)
0 40-72 45-78 0 65-85 0 65-85
1 73-112 79-117 1 86-109 1 86-110
2 113-157 118-161 2 110-137 2 111-135
3 158-207 162-209 3 138-167 3 136-165
4 208-260 210-261 4 168-199 4 166-200
5 261-318 262-317 5 200-234 5 Over 200


IMPORTANT NOTE ABOUT ENHANCED F-SCALE WINDS: The Enhanced F-scale
still is a set of wind estimates (not measurements) based on damage.
Its
uses three-second gusts estimated at the point of damage based on a judgment of
8 levels of damage to the 28 indicators listed below. These estimates vary with
height and exposure. Important: The 3 second gust is not the same wind as
in standard surface observations. Standard measurements are taken by weather
stations in open exposures, using a directly measured, "one minute
mile" speed.


Source: http://www.spc.noaa.gov/faq/tornado/ef-scale.html