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 water heats the air above
it, and the updrafts of warm, moist air begins 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 do 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 is 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 vapor. 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. As the updrafts speed up, air swirls faster and
faster around the storm center and 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 it 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" develops.
 
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. Tornado winds
cover only a small area, usually less than a mile across,
whereas the winds of a hurricane may cover an area 60 miles
wide out from the center of the eye. Another reason is that
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 Dorothy). In that time, it may
travel tens of thousands of miles over the sea and land.
 
At sea, hurricane winds whip up giant waves as high as 20
feet. 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 and there is havoc all
around.