Tornado Alley is located in the central part of the United States. Nowhereelse on the planet do the ingredients for these destructive storms cometogether with such frequency. Thunderstorms are triggered when air massesclash. When the speed and direction of the wind changes dramatically withaltitude (called wind shear), rotation develops in the overall atmosphere. Asthis rotation is entrained into a building thunderstorm cloud, the likelihoodof a tornado increases dramatically.It has been estimated that 100,000 thunderstorms occur across the United Stateseach year. Of those, less than 1 percent spawn tornadoes. Yet, tornadoes arethe most violent storms on the face of the Earth, and the larger ones take aterrible toll when they move across a populated area.
So far this year, there haven't been that many twisters. Just 82 have beensited so far as compared to the 383 tornadoes that occurred in 2009 fromJanuary through April. The season still has a long way to go, however, with Mayusually being the most prolific month.
Story by AccuWeather.com Senior Meteorologist John Kocet.
