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A tornado is a column of violently rotating air, spawned by a thunderstorm, which is connected from the thunderstorm cloud to the ground. It often appears funnel shaped or as a column of debris. Tornadoes are one of nature's most violent storms. They may develop suddenly, and may contain winds that reach over 250 mph. Tornadoes pose a significant threat to human life and are responsible for millions of dollars worth of property damage each year.

In 1971, Dr. Theodore Fujita developed a scale to categorize tornadoes based upon their intensity and area. In order to determine the intensity, the Fujita Scale relates a tornado's damage to the fastest quarter-mile wind speed at the height of a damaged structure. Over the years, problems have arisen with this scale. The scale is solely based upon the damage caused by a tornado, which makes it difficult to determine intensity when tornadoes move over an area with no structures. In addition, the scale does not take into account differences between structures based upon how they are constructed. To account for some of these problems, a modified version of the scale known as the Enhanced Fujita Scale was created and put into operation in 2007.

Fujita Scale vs. Enhanced Fujita Scale

Fujita Scale Enhanced Fujita Scale
F-Scale Fastest 1/4 Mile Wind Speed 3-Second Wind Gusts Type of Damage Done EF-Scale 3-Second Wind Gusts
F0 (Gale) 40 - 72 mph 45 - 78 mph Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards EF-0 65 - 85 mph
F1 (Weak) 73 - 112 mph 79 - 117 mph Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off roads EF-1 86 - 110 mph
F2 (Strong) 113 - 157 mph 118 - 161 mph Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated EF-2 111 - 135 mph
F3 (Severe) 158 - 207 mph 162 - 209 mph Roof and some walls torn off well constructed houses; trains overturned; most trees in forests uprooted EF-3 136 - 165 mph
F4 (Devastating) 208 - 260 mph 210 - 261 mph Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated EF-4 166 - 200 mph
F5 (Incredible) 261 - 318 mph 262 - 317 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 EF-5 > 200 mph

For more information regarding the Enhanced Fujita Scale, click here.


Sources and Additional Information

  US Tornado Climatology

Tornadoes by the Numbers>>