| Hurricane Anatomy
During the stages of development described in the previous page, certain
characteristics become more prominent as the hurricane increases in
strength. At the center of the hurricane is a 10-to-65-km-diameter cloud
free area of sinking air and light winds, called the eye. As air rises
in the surrounding thunderstorms, some of it is forced towards the center,
where it converges and sinks. As this air sinks, it compresses and warms
to create an environment (mostly) free of clouds and precipitation.
The eye is the calmest part of the storm because the strong surface
winds converging towards the center never actually reach the exact center
of the storm, but instead form a cylinder of relatively calm air. Like
an ice skater whose body spins faster as their arms are drawn inward,
air near the surface attempts to speed up as it spirals in towards the
center of the hurricane (known as the Law of Conservation of Angular
Momentum). Since the winds can't increase infinitely (a product of the
Law of Conservation of Energy), they must stop short of reaching the
center.
(Image
courtesy NOAA)
Bordering the eye of a mature hurricane is the eye wall, a ring of
tall thunderstorms that produce heavy rains and very strong winds. The
most destructive section of the storm is in the eye wall on the side
where the wind blows in the same direction as the storm's forward motion.
For example, in a hurricane that is moving due west, the most intense
winds would be found on the northern side of the storm, since the hurricane's
winds are added to the storms forward motion.
Surrounding the eye wall are curved bands of clouds that trail away
in a spiral fashion, suitably called spiraling rain bands. The rain
bands are capable of producing heavy bursts of rain and wind, perhaps
one-half or two-thirds the strength of those associated with the eye
wall.
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Hurricanes: The Greatest Storms on Earth
Hurricane
Beatriz had a well-formed eye on July 12, 1999, while she was in the
Pacific Ocean 800 miles off the coast of Mexico. (Image courtesy NOAA)
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