                     Hurricanes                      ==========          Hurricanes get their start over the warm tropical waters of the North   Atlantic Ocean near the equator. Most hurricanes appear in late summer or  early fall, when sea temperatures are at their highest. The warm waters  heats the air above it, and the updrafts of warm, moist air begin to rise.   Day after day the fluffy cumuli form atop the updrafts. But the cloud  tops rarely rise higher than about 6,000 feet.   At that height in the tropics, there is usually a layer of warm, dry air  that acts like an invisible ceiling or lid.       Once in a while, something happens in the upper air that destroys  this lid. Scientist don not know how this happens. But when it does, it's  the first step in the birth of a hurricane.       With the lid off, the warm, moist air rises higher and higher. Heat       energy, released as the water vapor in the air condenses. As it condenses  it drives the upper drafts to heights of 50,000 to 60,000 feet. The   cumuli become towering thunderheads.       From outside the storm area, air moves in over the sea surface to  replace the air soaring upwards in the thunderheads. The air begins   swirling around the storm center, for the same reason that the air   swirls around a tornado center.       As this air swirls in over the sea surface, it soaks up more and  more water vapour. At the storm center, this new supply of water vapor  gets pulled into the thunderhead updrafts, releasing still more energy  as the water vapor condenses. This makes the updrafts rise faster,   pulling in even larger amounts of air and water vapor from the storm's  edges. And as the updrafts speed up, air swirls faster and faster around  the storm center. The storm clouds, moving with the swirling air, form a  coil.             In a few days the hurricane will have grown greatly in size and  power. The swirling shape of the winds of the hurricane is shaped like a  dough-nut. At the center of this giant "dough-nut" is a cloudless, hole                                                                           usually having a radius of 10 miles. Through it, the blue waters of the  ocean can be seen. The hurricane's wind speed near the center of the   hurricane ranges from 75 miles to 150 miles per hour.        The winds of a forming hurricane tend to pull away from the center   as the wind speed increases. When the winds move fast enough, the "hole"  developes.       This hole is the mark of a full-fledge hurricane. The hole in the  center of the hurricane is called the "eye" of the hurricane. Within the  eye, all is calm and peaceful. But in the cloud wall surrounding the eye,   things are very different.       Although hurricane winds do not blow as fast as tornado winds, a  hurricane is far more destructive. That's because tornado winds cover  only a small area, usually less than a mile across. A hurricane's winds  may cover an area 60 miles wide out from the center of the eye. Another  reason is tornadoes rarely last as long as an hour, or travel more than  100 miles. However , a hurricane may rage for a week or more (example:  Hurricane Dorthy) In that time, it may travel tens of thousands of miles  over the sea and land.       At sea, hurricane winds whip up giant waves up to 20 feet high. Such   waves can tear freighters and other oceangoing ships in half. Over land,  hurricane winds can uproot trees, blow down telephone lines and power  lines, and tear chimneys off rooftops. The air is filled with deadly  flying fragments of brick, wood, and glass. 