LYCOS RETRIEVER 
Tornado: Tornado Alley
built 220 days ago
Florida is one and Tornado Alley is the other. Florida has a lot of tornadoes simply because it is home to almost daily thunderstorms. In addition, the Florida peninsula is often impacted by several tropical storms or hurricanes each year. When these tropical systems move ashore, the embedded thunderstorms in the rain bands often produce tornadoes. However, despite the violent nature of a tropical storm, the tornadoes they spawn (some being water spouts) tend to be weaker than those produced by non-tropical thunderstorms.
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In comparison with a cyclone or hurricane, a tornado covers a much smaller area but can be violent and destructive. The atmospheric conditions required for the formation of a tornado include great thermal instability, high humidity, and the convergence of warm, moist air at low levels with cooler, drier air aloft. Although tornadoes have occurred on every continent except Antarctica, they are most common in the continental United States, where tornadoes typically form over the central and southern plains, the Ohio valley, and the Gulf states. The area where the most violent storms commonly occur in the United States is known as Tornado Alley, which is usually understood to encompass the plains from N central Texas north to the Dakotas, with the peak frequency located in Oklahoma. A tornado typically travels in a northeasterly direction with a speed of 20 to 40 mi (32–64 km) per hr, but tornadoes have be reported to move in a variety of directions and as fast as 73 mi (117 km) per hr—or to hover in one place. The length of a tornado's path along the ground varies from less than one mile to several hundred.
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Most continents have regions where conditions for tornado formation are more likely to develop. In the USA, across a broad zone from Nebraska to Texas and Oklahoma, violent tornadoes develop more frequently than elsewhere. This region has been named ‘tornado alley’. In this zone cold dry air moving south and east from across the Rockies meets warm moist air from the Gulf of Mexico, especially in late spring and summer when the general conditions are optimum. On some remarkable occasions more than a hundred tornadoes have been recorded in a day, not only in the USA but ... in the British Isles. In the US on 3-4 April 1974 within sixteen hours in thirteen states from Georgia to the Canadian border there were 148 tornadoes, of which 48 caused 315 deaths.
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Norman, Oklahoma; data has been analyzed to show a historical representation of several smaller apparent tornado alleys across the United States as determined by a long track F3 to F5 tornadoes. A map of the United States from 1880 to 2003 was constructed showing normalized frequencies of F3 to F5 tornadoes with path lengths of at least 25 miles. This research gives a well needed upgrade to how we look at tornado prone areas in the US and I believe helps give a more accurate representation of areas not always known as tornado alley. I continue to believe most tornado alley maps do not represent the most dangerous areas in the US correctly, and have been vague in defining them to the public which may become a serious safety issue in the future. I continue to believe we need to go to maps showing multiple tornado alleys in the US and not ignore overwhelming evidence that many of the most violent tornado areas in the US have been left off tornado alley maps for too long. While it may be true that tornado frequency may be highest in a small area in the US on a yearly basis, dangerous and violent tornadoes happen over many tornado alley sections within the US that may have prolonged droughts of tornadoes before being annihilated by large, long lived tornadoes again and again. These small tornado alleys are seen when looking at the US by a county to county assessment. Below are the most dangerous counties in the US for F3 to F5 tornadoes with path lengths longer than 25 miles. Most of these dangerous counties are not listed on most tornado alley maps.
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Only one in a hundred thunderstorms produce a tornado. They happen quickly and often stay on the ground for only a few minutes. While Florida gets the most tornados of any state, a strip of land that extends from northeast Texas through Oklahoma, Kansas, Nebraska and Missouri has more tornadoes than any other place in the U.S. That area is called "Tornado Alley."
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In winter, tornado activity is usually confined to the Gulf Coastal Plain. In spring, the most active tornado season, tornadoes typically occur in central Tornado Alley and eastward into the Ohio Valley. In summer, most tornadoes occur in a northern band stretching from the Dakotas eastward into Pennsylvania and southern New York State.
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Tornado Alley