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.
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.
US Tornado Climatology