Fujita Scale

 Ted Fujita was the Japanese-born American meteorologist who in collaboration with Allen Pearson, created the Fujita Scale, or F-Scale, a system of classifying tornado intensity based on damage to structures and vegetation. He also discovered macro-bursts and micro-bursts, weather phenomena that are associated with severe thunderstorms and are hazards to aviation.

 The following are the scale numbers, wind speeds and damage that could be expected:

— F0 —

Gale tornado; 40-72 mph

 Some damage to chimneys; breaks branches off trees, pushes over shallow-rooted trees; damages sign boards

— F1 —

Moderate tornado; 73-112 mph

 The lower limit is the beginning of hurricane wind speed; peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off roads; attached garages may be destroyed

— F2 —

Significant tornado; 113-157 mph

 Considerable damage; roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated

— F3 —

Severe tornado; 158-206 mph

 Roof and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted

— F4 —

Devastating tornado; 207-260 mph

Well constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated

— F5 —

Incredible tornado; 261-318 mph

 Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 meters; trees debarked; steel-reinforced concrete structures badly damaged

— F6 —

Inconceivable tornado; 319-379 mph

 These winds are very unlikely. The small area of damage they might produce would probably not be recognizable along with the mess produced by F4 and F5 wind 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. If this level is ever achieved, evidence for it might only be found in some manner of ground swirl pattern, for it may never be identifiable through engineering studies.

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