topics weather 8481606 ----- # What is a tornado? ## Tornadoes come in many shapes and sizes, but typically form a condensation funnel, with its narrow end touching the ground. ![A huge tornado funnel cloud touches down in Orchard, Iowa][1] A huge tornado funnel cloud touches down in Orchard, Iowa Photo: AP 12:01AM BST 29 Apr 2011 Most have a wind speed of less than 110 mph and are around 250 feet across, travelling a few miles before dissipating. The most extreme however can attain wind speeds of more than 300mph and stretch more than two miles across. In the case of the Alabama tornado, it stretched a mile across, 20 times larger than the typical tornado. About one in every three is classified as "strong". About 30 per cent of all tornado deaths result from this category, while nearly 70 per cent result from "violent" tornadoes. "Violent" ones however are very rare - only about two per cent. It was also the deadliest tornado system since the "super outbreak" of April 1974, when 310 people were killed in 148 twisters across 13 states. Tornadoes can be found on every continent except Antarctica. But the vast majority occur in Tornado Alley in the US. Tornado Alley covers an area between the Rocky Mountains and the Appalachian Mountains, and consists of Texas, Oklahoma, Kansas, Nebraska, South Dakota and the Colorado Eastern Plains. ## Related Articles * [Tornado survival stories as America mourns][2] 30 Apr 2011 * [US storms: tornado blows shop sign 112 miles][3] 29 Apr 2011 * [US storms: bad weather threatens to delay Endeavour's final flight][4] 29 Apr 2011 * ['Catastrophic' tornadoes bring death to American south][5] 29 Apr 2011 * [Space shuttle launch delayed][6] 29 Apr 2011 [X][7] Share & bookmark Delicious Facebook Google Messenger Reddit Twitter Digg Fark LinkedIn Google Buzz StumbleUpon Y! Buzz [What are these?][8] * Share: [Share][7] [ ][9] [ ][10] [Tweet][11] http://www.telegraph.co.uk/topics/weather/8481606/What-is-a-tornado.html Telegraph ## [Weather][12] * ### [News »][13] * ### [World News »][14] * ### [North America »][15] * ### [USA »][16] * ### [Science News »][17] In topics [![][18]][19] ### [Weather forecast][19] [![Lacy Tasker salvages what she can from her mothers house after it was destroyed when a massive tornado passed through the town on May 24, 2011 in Joplin, Missouri][20] ][21] ### [Newest tornado pictures][21] [![A man carries a young girl who was rescued after being trapped with her mother in their home after a tornado hit Joplin, Missouri][22] ][23] ### [US Midwest tornadoes][23] [![Vehicles are stranded on a flooded road near Vicksburg, Mississippi][24] ][25] ### [Mississippi River floods][25] [![][26] ][27] ### [Deadly tornado in Alabama][27] [X][7] Share & bookmark Delicious Facebook Google Messenger Reddit Twitter Digg Fark LinkedIn Google Buzz StumbleUpon Y! Buzz [What are these?][8] Share: * [ ][7] * [ ][9] * [ ][10] * [Tweet][11] * Advertisement ![][28] Advertisement [EDITOR'S CHOICE »][29] ### [Gil Scott-Heron: 'A voice for Shakespeare'][30] [![Gil Scott-Heron][31]][30] Composer, musician, poet and author whose writing provided a vivid commentary on the black American experience. ### [Beekeeping diary: the new colonies arrive][32] ### [Spectacular light show dazzles Sydney][33] ### [WS Gilbert: a knight for our times][34] ### [The Telegraph's Matt is Hay Festival star][35] Advertisement Classified Advertising * [Services][36] * [Property][37] * [Motoring][38] Loading [Find your ideal job with Telegraph Jobs][39] var puffs_8120657 = new Array();