ASL What Is a Tornado?

Clarendon Learning explores Tornadoes. Legend has it that Pecos Bill, the toughest Texas cowboy ever, took his lasso made from a rattlesnake and roped the biggest meanest cyclone ever and rode that mean old cyclone until it got so tired that it petered out. And the story is told about how Dorothy and Toto were picked up in their house by a beast of a tornado and dropped over the rainbow in the land of Oz. These stories may be tall tales in fantasy and fun to tell around the campfire, but they're close in describing the power and fury of one of nature's most terrifying events, the tornado. Tornadoes, also known as twisters, also known as cyclones, are vertical funnels of rapidly spinning air. And though they can happen just about anywhere around the world, a great percentage of them happen right here in the United States. Welcome to Ground Zero, Tornado Alley. From South Dakota down through Nebraska, Kansas, Oklahoma, Texas, and over to Eastern Colorado, this is where many tornadoes in the U.S. occur, more than a thousand a year. With vortex action spinning up to 250 miles per hour, being in the neighborhood of an active tornado is no place you want to be unless you're a storm chaser. They like to chase thunderstorms and catch the actual birth of a tornado. Dangerous business, kids. Where do they come from? Do they pop up out of the ground? Well, no. Here's what happens. When warm moist air moving up from the Gulf of Mexico meets cool dry air coming down from Canada, a very unstable weather pattern develops. Thunderstorms and cumulonimbus clouds gather. If the storm pattern remains random and disorganized, scattered storminess will be the only result. But if the storm pattern is more organized and as rising warm air becomes cooled, the clouds begin to swirl. More warm air is sucked up from the ground. A funnel cloud begins to take shape. If it touches the ground, it's a full-on tornado. A tornado may be a few feet across or up to nearly two miles wide. It may be a water spout, a land spout, or a dust devil. They move along the ground at maybe 20 miles per hour, maybe faster. Some have been clocked at more than 70 miles per hour, and so they move shredding everything in their path. Houses become splinters. Cars and trucks tossed about like toys. Trees are uprooted. Hail the size of golf balls may begin to rain from the sky. The sound is unmistakable. The sound is like a roaring freight train, but there is no locomotive. The life expectancy of a tornado is about six to ten miles, and some have been much, much longer, as it leaves a swath of destruction in its path. It's very difficult to predict precisely when and where a tornado will strike. However, dark greenish skies and rotating clouds and hail are a pretty good sign. Supercells, tenacious and long-lasting storms create the most powerful tornadoes. The emergency broadcast system may issue a tornado watch, indicating that conditions are ripe for tornado weather, or a tornado warning, meaning that a tornado is likely, and you may have only 15 minutes to react and seek appropriate shelter. Through Tornado Alley, there are many emergency shelters prepared for this event, or you may have to seek the protection of a bathtub. Whoa! Here is an interesting piece of science. In the Northern Hemisphere, a tornado spins counterclockwise. In the Southern Hemisphere, tornadoes spin clockwise. I thought you'd find that interesting. Was I right? Tornadoes are graded as weak, strong, or violent. And now we come to the Enhanced Fujita Scale, the way tornadoes are rated based on the damage they cause. F0, light damage, a weak storm. F1, winds up to 112 miles per hour, moderate damage, a weak storm. F2, winds up to 157 miles per hour, considerable damage, a strong tornado. F3, winds up to 206 miles per hour, severe damage. F4, winds up to 260 miles per hour, devastating damage, considered a violent tornado. And if F4 isn't devastating enough, there is the F5, with winds over 261 miles per hour, causing incredible damage. A tornado is an amazing phenomenon. And remember, if you hear the roar of a locomotive, it may not be a train. Hope you had fun learning with us. Visit us at learnbright.org for thousands of free resources and turnkey solutions for teachers and homeschoolers.