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Huricane Structure
Contrary to how many weather maps appear, a hurricane is more
than a point on a weather map, and its path is more than a line.
It is a large system that can affect a wide area, requiring
that precautions be taken far from where the eye is predicted
to come ashore. This section talks about the different parts
of the hurricane and will help you better understand hurricane
hazards.
Hurricane Structure
The main parts of a hurricane are the rainbands on its outer
edges, the eye, and the eyewall. Air spirals in toward the center
in a counter-clockwise pattern, and out the top in the opposite
direction. In the very center of the storm, air sinks, forming
the cloud-free eye.
The Eye
The hurricane's center is a relatively calm, clear area usually
20-40 miles across. People in the midst of a hurricane are often
amazed at how the incredibly fierce winds and rain can suddenly
stop and the sky clear when the eye comes over them. Then, just
as quickly, the winds and rain begin again, but this time from
the opposite direction.
The Eyewall
The dense wall of thunderstorms surrounding the eye has the
strongest winds within the storm. Changes in the structure of
the eye and eyewall can cause changes in the wind speed, which
is an indicator of the storm's intensity. The eye can grow or
shrink in size, and double (concentric) eyewalls can form.
The Spiral Rainbands
The storm's outer rainbands (often with hurricane or tropical
storm-force winds) can extend a few hundred miles from the center.
Hurricane Andrew's (1992) rainbands reached only 100 miles out
from the eye, while those in Hurricane Gilbert (1988) stretched
over 500 miles. These dense bands of thunderstorms, which spiral
slowly counterclockwise, range in width from a few miles to
tens of miles and are 50 to 300 miles long. Sometimes the bands
and the eye are obscured by higher level clouds, making it difficult
for forecasters to use satellite imagery to monitor the storm.
Hurricane Size
Typical hurricanes are about 300 miles wide although they can
vary considerably, as shown in the two enhanced satellite images
below. Size is not necessarily an indication of hurricane intensity.
Hurricane Andrew (1992), the most devastating hurricane of this
century, was a relatively small hurricane.
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