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Wind and Deserts
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Roger Weller, geology instructor

by Karina Robinson
Physical Geology
Fall 2012

Tornadoes: Natural Disasters

How Tornadoes Form


     Tornadoes are natural phenomena that happen every year around the world.  Tornadoes are known to the most destruction around what is called the “Tornado Alley”.   Every couple of years, there is news about a new Tornado, the damage it caused and the many lives it took. Tornadoes may seem simple, but they are more complex than one thinks.


photo by Missouri department of public safety SEMA.


What is a tornado?
     It is a fast moving column of air usually descending from a thunderstorm.  Tornadoes are usually known as “twisters” because of its dark, smoky, churning appearance.   According to Kovach, “A tornado originally meant a violent squall (or gust of wind) blowing outward from the front of a thunderstorm along a portion of the West African coast, but today it usually refers to the type of extremely violent small diameter revolving storms found East of the Rock Mountains.


How does a Tornado form?

     It all starts with huge thunderstorms and air masses that come from three different sources.   And without the air and the huge, fluffy clouds that turn into thunderstorms tornadoes would not exist. These types of thunderstorms are called either single cell or super cell thunderstorms. The pictures below show the difference between a single cell (bottom) and a super cell (top).   A super cell tilts on its side because of the air masses and a single cell is stationary, the warm air just rises up while it is raining and hailing on the ground.   According to Abbott, the conditions for this air masses involve, “A northerly flow of marine tropical air from the Gulf of Mexico… humid and has temperatures at the ground in excess of 75 degrees Fahrenheit, a cold, dry air mass moving down from Canada or out from the Rocky Mountains at speed in excess of 50 miles per hour and lastly a jet-stream winds racing east at speeds in excess of 150 miles per hour” (Abbott 293). The temperatures of the cool and dry humid air masses are how thunderstorms are created. “A thunderstorm begins with an initial updraft of the warm, moist air…aided by wind pushing up a hill slope.  The moist air starts to rise high as the cool, dry air is descending rapidly”( Abbott, 284) causing the thunderstorm to tilt, letting rain to fall and for the tornado to start forming.  Within the tilt of the storm, winds and clouds will start to rotate or spiral in what looks like a vacuum tube coming out of the bottom of the super cell. 

Super Cell diagram from Wikipedia 

Single cell picture Alabama Weather Forecast office

 Where are Tornadoes found?

     Tornadoes are detected all over the world.  Tornadoes are not discriminate towards humankind at all.  They can be detected in Africa, Australia, and other parts of the world, but they are known more in the United States of America.   And it is usually happens in our Great Plains region also known as “Tornado Alley,” which includes states like Texas, Oklahoma, Missouri, Kansas and many more.   They are in the center of the U.S. and they host about 70 to 80 percent of all tornadoes.


How to determine Tornadoes?

     “A man by the name of Tetsuya Theodore Fujita was the first Japanese-American meteorologist that created the Fujita or F-Scale” (Britannica Encyclopedia).   He practically found a way to categorize or put in families the different types of tornadoes.   Like for example, he would categorize them by the damage it caused, how weak or severe the tornado was and he also gave it a number column to follow each tornado with.   And to this day, scientist and meteorologists are still using the same scale, but now it is more advanced in the categories.  These are the two charts side by side so you can see that they are same, but of course it has been modified since Fujita died.

fox news



Works cited

Abbott, Patrick. Natural Disasters. New York. San Diego State University. 2004.Print.

Kovach, Robert L. Earth’s Fury: An Introduction to Natural Hazards and Disasters. Englewood Cliffs, New Jersey. Prentice-Hall Inc. 1995. Print.

Learn more about Tornadoes. 27 November 2012. Web.