A tornado's winds usually blow from 75 mph to 300 mph. They can accelerate from nearly standing still to moving at almost 70 mph. Tornadoes become visible when a condensation funnel made of water vapor forms in extremely low pressure, or when a tornado lofts dirt, dust, and debris upward from the ground.

A tornado's diameter varies from tens of meters to nearly one mile. It's usually an average diameter of 160 ft. Tornadoes that form in the Northern hemisphere rotate counter clockwise around a center of low atmospheric pressure. In the Southern hemisphere, tornadoes blow clockwise from high atmospheric pressure.

A tornado begins with an intersection between a storm's updraft and winds. An updraft is a current of warm, moist air that rises upward through the thunderstorm. The updraft intersects with the winds, which must change the height in favorable ways for the interaction to occur. This interaction causes the updraft to rotate at the middle levels of the atmosphere. The rotating updraft stabilizes the thunderstorm and gives it its Super Cell characteristics.

In the United States, about 75% of all tornadoes are F0-F1, 21% are F2 or F3, and 1% of all tornadoes in the United States rank F4-F5. Only about 1 or 2 tornadoes a year reach F5. On the other hand, the F4 and F5 tornadoes account for 67 % of damage and fatalities caused by tornadoes.

The National Weather Service alerts the Public to severe weather

In 1971, Theodore Fujita, a Meteorology professor at the University

If a tornado warning is issued, you should seek shelter immediately in a basement or interior portion of a building. Mobile homes and cars should be abandoned because they may roll in high winds. If caught outside, you should cover your head from debris with your hands lye flat on the ground.

The worst and most powerful tornadoes in the U. S. have claimed hundreds of lives. On March 18, 1925, the Tri-state outbreak occurred killing 740 people with 7 tornadoes occurring in Illinois, Missouri, and Indiana. Another deadly tornado outbreak in the United States was the Super Outbreak of April 3-4, 1974. It spawned 148 tornadoes and killed 315 people from Northern Alabama to Ohio.

In central U. S. lies a region known as tornado alley where most tornadoes occur worldwide. Tornadoes usually occur between late Spring and earl

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