Reported May 2006

BACKGROUND: The National Oceanic and Atmospheric Administration, or NOAA, has a new weather plane to help scientists learn more about weather patterns and where and when hurricanes or tornadoes will strike. The aircraft carries remote sensors that use microwaves to probe the inside of an eye of a hurricane, which measures changes in vertical air currents, electrical activity, and the amount of ice contained in the highest thunderstorm clouds. These are all indicators of a hurricane's intensity and potential for destruction.

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 wind speeds surpass 74 MPH. Each 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 while 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 on the Saffir-Simpson Hurricane scale according to the strength of their winds. They are rated from lowest wind speeds (Category 1) to highest (Category 5). Don't let the category number fool you; even lower category storms can cause a great deal of damage. The damage is often caused by the storm surges and the resulting flooding, which is when water is pushed towards the shore by strong winds and combines with normal tides to create hurricane storm tides. The worst devastation from hurricane Katrina, for example, occurred when flooding caused the New Orleans levees to fail.

EFFECTS OF CLIMATE CHANGE: If it seems like hurricanes are becoming more frequent and severe, that's because they are. Thanks to rising air and water temperatures around the world it is easier for hurricanes to form. Some scientists attribute this to global warming and human activity, such as deforestation and greenhouse gas emissions. Others think it is due to natural changes deep in the Atlantic Ocean, part of a natural cycle that shifts every 40 to 60 years.

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

If you would like more information, please contact:

National Hurricane Center
11691 S.W. 17th Street
Miami, FL 33165-2149
(305) 229-4404

The American Meteorological Society
45 Beacon Street
Boston, MA 02108-3693
(617) 227-2425
http://www.ametsoc.org

FACTOID...

In an average three-year period, roughly five hurricanes strike the United States coastline, killing 50 to 100 people anywhere from Texas to Maine.

ON THE WEB ...

http://nhc.noaa.gov