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Beaufort Wind Scale

0 --- Calm less than 1 mph Smoke rises vertically
1 --- Light air 1 - 3 mph Smoke drifts with air, weather vanes inactive
2 --- Light breeze 4 - 7 mph Weather vanes active, wind felt on face, leaves rustle
3 --- Gentle breeze 8 - 12 mph Leaves & small twigs move, light flags extend
4 --- Moderate breeze 13 - 18 mph Small branches sway, dust & loose paper blows about
5 --- Fresh breeze 19 - 24 mph Small trees sway, waves break on inland waters
6 --- Strong breeze 25 - 31 mph Lagre branches sway, umbrellas difficult to use
7 --- Moderate gale 32 - 38 mph Whole trees sway, difficult to walk against wind
8 --- Fresh gale 39 - 46 mph Twigs broken off trees, walking against wind very difficult
9 --- Strong gale 47 - 54 mph Slight damage to buildings, shingles blown off roof
10 -- Whole gale 55 - 63 mph Trees uprooted, considerable damage to buildings
11 -- Storm 64 - 73 mph Widespread damage, very rare occurrence
12 -- Hurricane over 73 mph Violent destruction


The Fujita Scale


Tornadoes are measured using a scale that measures the amount of damage the tornado causes. The scale is known as the "Fujita Tornado Intensity Scale":

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 the 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


[quoted from Tornado Project]


Between 1950 and 1994, 74% of all of the tornadoes that touched down in the United States were "weak" (F0 or F1), 25% were "strong" (F2 or F3), and only 1% were "violent" (F4 or F5).

Note: Above table may contain errors and should be used only at your own risk. The abbreviation "mph" signifies "miles per hour."

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