Inigo

In the film, it appears like a black funnel on the horizon, between the dark clouds and the prairie. The sky gets grayer and grayer. The wind shrieks and wails. Auntie Em calls frantically for Dorothy as debris blows around the farmyard. While the others are forced to flee to the storm cellar, terrified Dorothy is trapped in the house alone. She is caught in the whirlwinds. A flying window frame knocks her out. When Dorothy wakes up, the storm has lifted the farmhouse into the sky like a balloon.L. Frank Baum’s book The Wonderful Wizard of Oz opens with a tornado whirling through the Kansas prairie. The 1939 MGM Wizard of Oz musical calls the storm a “twister.” Whatever the name, when one of these storms strikes, it can be incredibly destructive. Quite simply, a tornado is a spinning column of air that reaches from a storm cloud to the ground. But there’s nothing simple about tornadoes. Scientists do know a few basic things: the biggest and most dangerous twisters form inside powerful thunderstorms called supercells. Most tornadoes are small and weak, and last only a few minutes. But a few tornadoes are mile-wide whirlwinds that last for hours. Scientists measure a tornado’s wind speed and destructive power on the Fujita scale, created by tornado scientist Ted Fujita. The Fujita scale is used to rate the intensity of a tornado by examining the damage caused by a tornado after it has passed over a man-made structure.Some Fujita tables also list an F6 tornado. It would be a terribly destructive storm, sending even huge objects like cars flying. An F6 has never been seen. There’s still a lot to learn about tornadoes. For one thing, scientists aren’t exactly sure how they form. Supercells grow when a warm, wet air mass meets a cool air mass. The warm air rises sharply and hits twisting winds high in the atmosphere. This sets the storm spinning. The rotation gets smaller and faster, as when a figure skater pulls in her arms to spin. Sometimes, this spinning reaches the ground, and a tornado forms. Scientists also aren’t sure why some storms make tornadoes and others don’t. It’s hard to study tornadoes while they are active, because scientists can’t get close to them without risking their lives. Instead, they use sophisticated instruments. Doppler radar measures the speed and direction of blowing droplets of water. Computer models can recreate tornado formation.In the 1980s, scientists tried to put a container covered with thousands of special weather sensors into the path of a tornado. They hoped the sensors would be able to measure what was happening. They named it the Totable Tornado Observatory, or TOTO, after Dorothy’s beloved dog. Scientists stopped using TOTO in 1987, because it never really worked as planned. “There’s no place like home,” Dorothy says in The Wonderful Wizard of Oz. For Dorothy, home is the state of Kansas. And there’s no place like Kansas for tornado scientists. The state is right in the middle of what’s called Tornado Alley. This area of the United States sees more tornadoes than anywhere in the world.Tornadoes can happen in all fifty states. But they are much more common in Tornado Alley. Tornado Alley is a general area covering much of Texas, Oklahoma, Kansas, Iowa, and Nebraska. It also includes parts of Colorado, Minnesota, and South Dakota. Since people began keeping records, they have spotted over 2,000 tornadoes each in Oklahoma and Kansas, and over 5,000 in Texas. By comparison, the northeastern state of Connecticut has had only 61 tornadoes. Compared to the rest of the world, that’s still a lot of tornadoes. The United States has about 1,000 a year, on average. The United States also sees the strongest ones. Tornadoes with a rating of F3 or greater on the Fujita scale are very rare outside the United States. The country with the second-most tornadoes, Canada, has only about 100 per year. So what makes Tornado Alley so great for tornadoes? Tornadoes form inside powerful thunderstorms called supercells. And supercells happen when warm, humid air meets cold, drier air in the atmosphere. The position and shape of North America help create just these conditions in Tornado Alley. During the spring and summer, warm, wet air moves over the continent from the Gulf of Mexico. Meanwhile, the high, cold Rocky Mountains send cold air swirling down from the West. Year after year, these air masses collide and produce violent thunderstorms and tornadoes.Residents of Tornado Alley need to be ready for these strong storms. The National Weather Service put its National Storm Prediction Center in Norman, Oklahoma, right in the middle of Tornado Alley. Scientists there watch the skies and keep careful track of strong storms. They are responsible for issuing tornado watches and tornado warnings. During a tornado watch, conditions are right for a tornado to form, though one hasn’t happened yet. During a tornado warning, a tornado has definitely been spotted and is on the way. Some areas have loud sire