A tornado (often referred to as a twister or, erroneously, a cyclone) is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust. Most tornadoes have wind speeds less than 110 miles per hour are approximately 250 feet across, and travel a few miles (several kilometers) before dissipating. Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes in the world occur in the Tornado Alley region of the United States, although they can occur nearly anywhere in North America.[6] They also occasionally occur in south-central and eastern Asia, the Philippines, northern and east-central South America, Southern Africa, northwestern and southeast Europe, western and southeastern Australia, and New Zealand.
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Various types of tornadoes include the landspout, multiple vortex tornado, and waterspout. A multiple-vortex tornado is a type of tornado in which two or more columns of spinning air rotate around a common center. A waterspout is defined by the National Weather Service as a tornado over water. Fair weather waterspouts are less severe but far more common, and are similar to dust devils and landspouts. They occur
