Tornado

A tornado is a violent rotating column of air extending above from a thunderstorm to the ground. You need warm, moist air from the Gulf of Mexico and cool, dry air from Canada. When those two meet, they cause instability in the atmosphere.  Tornadoes have been observed on every continent except Antarctica.  The vast majority of tornadoes occur in the Tornado Alley region of the United States.  Tornadoes come in many shapes and sizes, but they are typically in the form of a visible funnel whose end touches earth and is often encircled in a cloud of debris and dust.  Though tornadoes can strike in an instant, there are precautions  people can take to survive one.  You should have a pre-determined plan if you live in a tornado prone area.  Underground refuges have saved thousands of lives. If you do not have a shelter, getting low in a ditch or low spot on the ground is your next best option.  Never go under a highway overpass as wind speed and funneling of debris can fly under the overpass and cause great injury. Tornadoes have been known to cross major rivers and climb mountains. As a general rule no area is safe from a tornado if you live in a tornado prone zone.