Analysis of wind field variations of major hurricanes in the Gulf of Mexico

In the public broadcast of tropical cyclone advisories, the wind field of a hurricane is often overshadowed by the maximum sustained wind speed (MSW). While the most extreme wind and surge impacts of a hurricane are confined to the small area where the MSW exists, and presents the greatest risk to the population located at the point of landfall, the circulating wind field of a large hurricane can bring significantly damaging wind and surge far away from the center of the hurricane. The environment of the Gulf of Mexico often allows tropical cyclones to attain or maintain major hurricane status, whereas the relatively small size of the Gulf allows for the effects of a large hurricane to be felt over much of the adjacent land area.

Tropical cyclones of 1992-2008 that were classified as a major hurricane at some time while positioned over the Gulf of Mexico are examined. Of the 15 cyclones, 14 experienced at least a 25% expansion of the 34-kt wind field while the cyclone center was situated over the Gulf of Mexico, with the lone exception being Hurricane Charley (2004). Of the 14 cyclones that expanded in size, 7 experienced at least a 95% expansion of the 34-kt wind field. Additionally, 9 of 14 cyclones expanded in size primarily while undergoing intensification. Most notably, the 34-kt wind field of Hurricane Katrina (2005) increased over eight-fold in area over the Gulf of Mexico, with virtually all of the expansion taking place as the hurricane intensified from a Category-1 to a Category-5.

Pertaining to Gulf cyclones, this study attempts to address the following questions: 1) Does cyclone intensification necessarily affect the size of the cyclone wind field? 2) What external features or processes control the total area, and the rate of expansion (i.e. dA/dt), of the wind field? 3) To what extent is storm surge affected by dA/dt versus total wind field area?