NOAA 99-R516
Contact: Erica Van Coverden


Rapid Intensification of hurricanes just before landfall presents a serious problem to National Hurricane Center (NHC) forecasters and regional emergency managers. Hurricanes that pass over deep warm-water pools can become grave threats to human life and property, as happened when 1995's Opal intensified from a category 2 to a category 4 hurricane in only 14 hours. This hurricane season, National Oceanic and Atmospheric Administration and University of Miami scientists will study rapid intensification caused by evaporation from a large warm-water eddy in the Gulf of Mexico.

Starting August 3, Dr. Peter Black, of NOAA's Atlantic Oceanographic and Meteorological Laboratory (AOML) in Miami, FL, and Dr. Lynn Shay of the University of Miami's Rosenstiel School for Marine and Atmospheric Science (RSMAS) will direct a joint effort to study the warm eddy by deploying expendable ocean sensors from NOAA airplanes flying over the Gulf of Mexico. The August 3-5 aircraft flights will take the eddy's pulse, deploying probes funded by the National Science Foundation to measure ocean currents, density, and temperature to a depth of 3,000 ft.

"Major hurricanes (winds stronger than 115 mph) cause 80% of all hurricane related damage, and rapid intensification causes major hurricanes. What we don't know are all the factors that can cause rapid intensification," says Dr. Hugh Willoughby, Director of the Hurricane Research Division at AOML, "But what we do know is that warm eddies were a factor in some memorable Gulf storms."

The reason the eddies cause rapid hurricane intensification in the Gulf of Mexico is that they are pockets of heat energy stored in the warm ocean waters. Black and Shay want to study the deep warm water eddy now forming from the Loop Current, a stream of warm Caribbean water that enters the Yucatan Straits, meanders northward almost to the Gulf Coast, and exits into the Florida Straits after a sharp turn around the Florida Keys.

"We believe that eddies like this one were the cause of rapid intensification in Opal (‘95), Camille (‘69), and several other Gulf hurricanes," said Black, "Should a hurricane cross this year's eddy, we will measure not only the change in eddy characteristics, but measure the physical characteristics of the atmospheric environment around the storm. In this way we hope to discover the relative importance of the ocean eddy and environmental wind shear in determining hurricane intensity change."

A warm eddy such as the one present in the Gulf this summer is a tremendous source of energy to a storm that passes over it. The hurricane winds draw heat from the water to fuel the storm, mixing the warm upper water with the cooler waters below as the storm passes by. Because the layer of warm water is so thick in the eddy, the ocean surface there is less susceptible to storm-induced cooling than it is outside the eddy.

Black and Shay hope that data gathered during this study will enhance knowledge and predictability of major hurricanes, which translates to increased warning time and better coastline preparedness.

"We look at a major hurricane in the Gulf with mixed emotions. It can't get out without destroying some coastal real-estate. On the other hand, the only way to learn exactly how the ring affects rapid intensification requires that a hurricane passes over the eddy," said Willoughby.

The study will entail several flights in WP-3D aircraft, operated by NOAA'a Aircraft Operations Center. This plane has been used by NOAA scientists for 25 years to study atmospheric conditions in and around hurricanes. Dropwindsonde instruments launched in the storm's environment from NOAA's new Gulf Stream - IV jet surveillance aircraft will measure atmospheric winds, pressure, temperature and humidity as they fall to the ocean's surface.

NOAA's mission is to describe and predict changes in the Earth's environment, and conserve and wisely manage the Nation's coastal and marine resources.