Understanding How Tornadoes Work
18 April 2011
Nathaniel Ramey comforts Megan Hurst at her grandmother's house in Askewville, North Carolina, after a tornado on Saturday
KATHERINE COLE: This is SCIENCE IN THE NEWS in VOA Special English. I'm Katherine Cole.
BOB DOUGHTY: And I'm Bob Doughty. This week, we will tell about the science of tornadoes. Tornadoes have been observed inwmany parts of the world. But the storms are most often found in the United States.
(MUSIC)
BOB DOUGHTY: Tornado season has begun in the United States. Violent storms struck several parts of the country last week. The National Weather Service said there were ten reports of tornadoes across the central and southern Plains states last Thursday.
A tornado is a violently turning tube of air suspended from a thick cloud. It extends from a thunderstorm in the sky down to the ground. The shape is like a funnel: wide at the top, narrower at the bottom.
Tornadoes form when winds blowing in different directions meet in the clouds and begin to turn in circles. Warm air rising from below causes the wind tube to reach toward the ground. Because of their circular movement, these windstorms are also known as twisters.
A huge funnel cloud touches down in Orchard, Iowa, on June 10, 2008
The most severe tornadoes can reach wind speeds of three hundred twenty kilometers an hour or more. In some cases, the resulting paths of damage can stretch more than a kilometer wide and eighty kilometers long.
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