Tornadoes

John F. Brosio (All rights reserved. Not for reuse)

A tornado is a destructive moving vortex of violently rotating winds that look like a funnel-shaped cloud and advance beneath a large storm system. The word originated in the mid-16th century, describing a thunderstorm in the Atlantic Ocean. It likely combines the Spanish words tronada (thunderstorm) and tornar (to turn).

• Tornadoes occur on all continents except Antarctica. The United States is the country with the highest frequency. With over 100 recorded tornadoes, Oklahoma City has been hit by more than any other city.
• Tornado Alley, according to the Glossary of Meteorology , is a term the media often use to denote a zone in the U.S. Great Plains region where tornadoes are most frequent. It includes North Texas, Oklahoma, Nebraska, and Kansas. In the spring, high-altitude cool air passes over the Rocky Mountains, then drops and warms up as it travels over the plains. This heated dry air draws warm, moist tropical air from the Gulf of Mexico. Scientists don’t fully understand how tornadoes form. They typically develop thousands of feet above the earth’s surface inside a severe rotating thunderstorm, called a “supercell thunderstorm.”
• In 1971, T. Theodore Fujita, a meterologist at the University of Chicago, created a scale to rate the severity of tornadoes. With support from Allen Pearson, director of the National Severe Storm Forecast Center of the National Oceanic and Atmospheric Administration, it became the standard. In 2007, the Enhanced Fujita Scale was developed. The six-step scale estimates wind intensity by measuring the amount of damage to the objects in a tornado’s direct path. It ranges from EF0 (light damage, with tree limbs and roof shingles torn off) to EF5 (incredible damage, with houses leveled to their foundations and the debris swept away). Nicknamed “Mr. Tornado,” Fujita did not see his first tornado until 1982, when he was 61 years old, in Colorado.
• The first known photograph of a tornado was taken in 1884, about 20 miles southwest of Howard, S.D.
• About 60 people are killed each year because of tornadoes in the United States, usually by flying or falling debris. Over a period of 21 hours, 3-4 May 1999, 74 tornadoes touched down across Oklahoma and Kansas.
• The deadliest tornado in U.S. history hit Missouri around midday on 18 March 1925 and crossed through Illinois into Indiana. This Tri-State Tornado, which set the record for the longest continuous track (219 miles), killed 695 people.
• The costliest tornado on record, rated EF5, touched down in Joplin, Mo., on 22 May 2011. It caused an estimated $2.8 billion in damages.