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Bracing for the Worst: Hurricane Help

Geologists Design Better Hurricane Forecasts

July 1, 2004

Researchers have designed a new rating system that forecasts with greater detail what will happen when a hurricane moves to land. Called the Hurricane Impact Scale, it takes into account the interaction of the hurricane with the coast, such as storm surge, or the amount of water pushed towards shore by the winds.

Why do hurricanes cause so much damage?

Science behind the news is funded by a generous grant from the NSF

Hurricanes can be extremely violent storms. Intense winds, heavy rains and flooding can level a coastal town and cause significant damage even to inland cities. For instance, a major hurricane will dump dozens of inches of rain within a couple of days, creating inland flooding.

The high, sustained winds cause structural damage, and are capable of rolling over cars and felling trees, and even eroding beaches. The strong winds can also push a wall of water, called a storm surge, in front of the storm, and if this happens at the same time as high tide, flooding and beach erosion. And hurricane winds have been known to spawn tornados, smaller, more intense cyclonic storms that can cause even more damage.

The extent of damage caused by a hurricane depends on its category (see sidebar), whether the storm comes ashore or merely grazes the coastline, and whether the right or left side of the hurricane strikes a given area.

Wind speed and the storm's speed-of-motion work together on the right side of the storm, but on the left, the speed of motion is opposite of the wind speed.

A Category-1 hurricane only causes minimal damage, mostly felling tree branches and uprooting mobile homes and other objects not anchored to the ground. A Category-4 hurricane will destroy mobile homes, while Category-5 hurricanes can destroy entire buildings.


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Did you know?...

In 1996, Hurricane Fran damaged or destroyed tens of thousands of homes in Raleigh, North Carolina. Damage was estimated in the billions of dollars.

More information on this story

Martha J. Heil
mheil@aip.org
American Institute of Physics
Tel: 301-209-3088