Resources: Mastery Test 1
Select the correct text in the passage.
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The Great Whirlwind
The tornado-or twister, as it is commonly called is one of the most feared of all meteorological events. Every year scenes of horrendous
damage appear on our television screens to reinforce that fear.
This article explores the origination of this destructive and deadly storm. In addition, you will learn how you can best protect yourself should
you find yourself in a tornado's path.
The Birth of a Whirlwind
The giant whirlwind known as a tornado arises out of the formation of a cumulonimbus cloud, an enormous collection of vapor that can be as
much as 40.000 feet high. A cumulonimbus cloud can generate a thunderstorm.
Thunderstorms occur when a warm air mass converges on a cold one. The warm air rises to meet the cold air, causing a series of updrafts
and downdrafts. For a while, raindrops are held up by the updraft in the cumulonimbus cloud, but eventually the drops combine until they
are too heavy for the updraft to support. The result is the development of heavy rain, lightning, strong winds, and perhaps hail.
A severe thunderstorm can produce a tornado-a rotating column of air that generates a funnel cloud extending to the earth's surface.
Usually a tornado doesn't stay on the ground for more than a few minutes. In fact, many funnel clouds never touch ground. Tornadoes can
also occur over water. These storms are called waterspouts.
Tornadoes occur more frequently in the U. S. than in any other part of the world. The central part of the country is the most affected area due
to the collision of cold and warm air masses in the spring months. As the warm, humid air from the Gulf of Mexico moves northward, the area
of highest frequency of tornadoes moves with it. Thus, in February most tornadoes are in the central Gulf states; in March and April most are
in the southeastern Atlantic states, and in May and June most are in the area going north from the southern Plains to the Great Lakes states.
Strength and Severity