Hurricane and Tornad

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Sometimes really violent thunderstorms spawn tornadoes. A tor- nado is a narrow, rapidly spinning column of air extending downward from a cumulonimbus cloud. Condensing water vapor and debris lifted into the air by the low­pressure center usually creates a visible funnel. Hurricanes, tropical storms, and convective storms created by strong cold fronts can produce tornadoes. These devastating rotating storms occur over all continents except Antarctica, but they are most common and destructive in the southern and central sections of the United States—an area called Tornado Alley.

​Dr. Pearson further improved the original Fujita scale by adding indicators that describe the width of the destruction path and the distance that the tornado was in contact with the ground. Low pressure within the funnel of a tornado is not the destructive force it once was thought to be. In 2003, a researcher successfully placed a pressure-recording instrument in the path of an F4 tornado that measured a pressure drop of only 0.1 atm. Pressure inside even a powerful tornado is just a little lower than at sea level. So tornadoes don’t cause buildings to explode in low pressure. Other research and field observations have shown that a tornado’s high winds simply push the building’s windward walls inward. The tornado’s updraft lifts the roof off the building. The other walls fall outward due to the winds.

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