The Fujita Scale is used to rate the intensity of a tornado by examining the damage caused by the tornado after it has passed over a human-made structure. According to the National Weather Service, it has made changes to the original Fujita Scale which came into effect in February 2007. Besides altering the wind speeds defining the categories, the new system classifies tornadoes based on damage to eighteen other types of structures, including trees, mobile homes and other types of buildings. The old system rated tornadoes only based on damage to homes.
The Fujita Scale (Original Scale)
Damages chimneys; Breaks branches off trees; Pushes over shallow-rooted trees; Damages sign boards.
Peels surface off roofs; Pushes mobile homes off foundations or overturns them; Pushes moving autos off the roads; May destroy attached garages.
Considerable damage. Tears roofs off frame houses; Demolishes mobile homes; Pushes boxcars over; Snaps or uproots large trees; Light objects become missiles.
Tears of roof and some walls off well-constructed houses; Overturns trains; Uproots most trees in forest.
Levels well-constructed houses; Blows structures with weak foundations off some distance; Throws cars; Large objects become missiles.
Lifts strong frame houses off foundations and carrys them considerable distances to disintegrate; Tosses automobile-sized objects through the air in excess of 100 meters; Debarks trees; Badly damages steel reinforced concrete structures.
Such winds are highly unlikely. The small area over which the damage they might produce would probably not be recognizable within the mess produced by F4 and F5 winds that would surround the F6 winds. Missiles, such as cars and refrigerators, would do serious secondary damage that could not be directly identified as F6 damage.
Wind Speed Estimates for the Original and Enhanced Fujita Scales for Tornado Damage (Implemented In US, February 2007)
ORIGINAL FUJITA SCALE
DERIVED EF SCALE
OPERATIONAL EF SCALE
Fastest 1/4-mile (mph)
3-Second Gust (mph)
3-Second Gust (mph)
3 Second Gust (mph)
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. (Click here for list of indicators). 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.
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