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A Connection Between Tornadoes and Cities?

UPDATED February 26, 2007

By WeatherBug Meteorologist, Ryan Towell

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Tornadoes don`t hit cities.

That is just one of many myths about Mother Nature`s most mysterious and terrifying phenomenon.

Although there is much that scientists do not know about severe storms and tornadoes, one thing is for certain; large cities are not immune to these destructive monsters.

Here are several recent examples where tornadoes and cities have clashed, with deadly results.

An F-2 tornado with winds of between 113 and 157 miles per hour slammed into downtown Fort Worth, Texas on March 28, 2000. Skyscrapers were heavily damaged and nearly demolished, cars were overturned and 4 people lost their lives as the twister roared into the western parts of that city during the evening rush hour around 6:18 p.m.

On the afternoon of August 11, 1999 and without warning, an F-2 twister pummeled downtown Salt Lake City. At least 100 were injured and one person was killed as the tornado flipped cars, toppled trees and sent glass and other debris flying through the busy downtown area during the lunch hour. This was Utah`s most destructive tornado, ever.

There were several additional instances of tornadoes hitting U.S. cities in 1999. On May 3 an F-5 tornado, the very top of the Fujita scale, with winds of between 261 and 318 miles per hour barreled into the southern sections of Oklahoma City. At least 40 were killed in Oklahoma on that day.

Over the years, tornadoes have made direct strikes on many other cities including Nashville, St. Louis, Kansas City and Miami.

The vast majority of tornadoes that touch down in this country every year are considered weak. In contrast, when tornadoes have hit major cities, the twisters were in most cases strong. Several theories have been proposed to explain why weak tornadoes in cities are a somewhat rare occurrence.

Ted Fujita, famed University of Chicago tornado researcher from which the tornado damage F-scale was created, suggested the reason that small tornadoes are seldom observed in large cities may have something to do with the urban heat-island effect. Turbulent, rising air flow produced by intense heating of the concentrations of concrete, steel and brick found in large cities may disrupt air flowing into a thunderstorm, thus preventing smaller funnels.

Another factor that may or may not reduce the number of small, weak tornadoes in cities may be increased friction and disruptive wind flows produced from buildings.

Research efforts continue into discovering what effects cities have on severe thunderstorms and tornadoes. There is still much that is unknown.

It is clear, however, that urban areas are not spared the threat of deadly twisters. The potential obstacles to weak tornadoes may do little to thwart large, destructive tornadoes from entering a city.

Tornadoes have in the past and will most certainly in the future make their way into heavily populated-areas of the U.S.

The story image depicts a tornado threatening Dallas, Texas on May 26, 1981 and is courtesy of NOAA.

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