'Tornado Season' Begins in the United States, Part 1

BARBARA KLEIN: This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein. BOB DOUGHTY:And I'm Bob Doughty. This week, we will tell about the science of tornadoes. Tornadoes have been observed in many parts of the world. But the storms are most often found in the United States. BARBARA KLEIN: Tornado season has begun in the United States. More than sixty tornadoes were reported in the country's southeast during the last weekend in April. One tornado measuring more than a kilometer wide struck the state of Mississippi. It destroyed homes, blocked roads and cut off electricity. The storms were blamed for ten deaths in Mississippi, and two others in nearby Alabama. Weather experts believe it was the most intense tornado event since two thousand eight. BOB DOUGHTY: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. 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. BARBARA KLEIN: With a tornado, bigger does not necessarily mean stronger. Large tornadoes can be weak. And some of the smallest tornadoes can be the most damaging. But no matter what the size, tornado winds are the strongest on Earth. Tornadoes have been known to carry homes, cars and trees from one place to another. They can also destroy anything in their path. Tornadoes have been observed on every continent except Antarctica. But experts say they are most commonly seen in the United States. On average, eight hundred tornadoes are reported nationwide each year. The National Oceanic and Atmospheric Administration keeps records of tornado sightings. It says tornadoes kill eighty people and injure one thousand five hundred others nationwide in an average year. Source: Voice of America