Reported September 2008

Why Do Hurricanes Cause So Much Damage?: 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, 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, which can cause flooding and beach erosion. Hurricane winds have been known to spawn tornados: smaller, more intense cyclonic storms that can cause even more damage.

About Hurricanes: A hurricane is a type of tropical cyclone; a low-pressure system that usually forms in the tropics and has winds that circulate counterclockwise near the earth's surface. Storms are considered hurricanes when their wind speeds surpass 74 MPH. Every hurricane arises from the combination of warm water and moist warm air. Tropical thunderstorms drift out over warm ocean waters and encounter winds coming in from near the equator. Warm, moist air from the ocean surface rises rapidly, encounters cooler air, and condenses into water vapor to form storm clouds, releasing heat in the process. This heat causes the condensation process to continue so that more and more warm moist air is drawn into the developing storm, creating a wind pattern that spirals around the relatively calm center, or eye, of the storm, much like water swirling down a drain. The winds keep circling and accelerating to form a classic cyclone pattern.

Rating Hurricanes: Hurricanes are categorized according to the strength of their winds according to the Saffir-Simpson Hurricane scale. They are rated from lowest wind speeds (Category 1) to highest (Category 5). But even lower category storms can cause a great deal of damage, mostly from storm surges and the resulting flooding. The worst devastation from hurricane Katrina, for example, occurred when flooding caused the New Orleans levees to fail.

The American Meteorological Society and the American Society of Civil Engineers contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

Aaron Hoover
Public Affairs
University of Florida
(352) 392-0186
ahoover@ufl.edu

American Meteorological Society
(617) 227-2425
http://www.ametsoc.org

Joan Buhrman
The American Society of Civil Engineers
(703) 295-6404
http://www.asce.org
jbuhrman@asce.org