A Study of Large-Scale Surface Fluxes and Vertical Motions Associated with Landfall of Hurricane Katrina

We investigated the possible relationship between the large-scale heat fluxes and intensity change associated with the landfall of Hurricane Katrina. After reaching the category 5 intensity on August 28th, 2005 over the central Gulf of Mexico, Katrina weakened to category 3 before making landfall (August 29th, 2005) on the Louisiana coast with maximum sustained winds of over 110 knots. We also examined the vertical motions associated with the intensity change of the hurricane. The data on Convective Available Potential Energy (CAPE), sea level pressure, and wind speed were obtained from the Atmospheric Soundings and NOAA National Hurricane Center (NHC), respectively for the period of August 24 to September 3, 2005. We developed an empirical model and a C++ program to calculate surface potential temperatures and heat fluxes using the above data. We also computed vertical motions using CAPE values. The study showed that the large-scale heat fluxes reached maximum (7960W/m2) with the central pressure 905mb. The Convective Available Potential Energy (CAPE) and the vertical motions peaked 3-5 days before landfall. The large vertical atmospheric motions associated with the land falling hurricane Katrina produced severe weather including thunderstorms and tornadoes.