HR: 0800h
AN: A21C-0649    [Abstracts]
TI: Influence of Loop Current on Hurricane Katrina in a High-Resolution Coupled Model
AU: * Lee, C
EM: chiaying@orca.rsmas.miami.edu
AF: University of Miami ---- RSMAS, 4600 Rickenbacker Causeway RSMAS/MPO, Miami, FL 33149, United States
AU: Chen, S S
EM: schen@orca.rsmas.miami.edu
AF: University of Miami ---- RSMAS, 4600 Rickenbacker Causeway RSMAS/MPO, Miami, FL 33149, United States
AB: Recent observational and numerical modeling studies have shown that coupled atmosphere-wave-ocean models may lead to substantial improvement in prediction of hurricane intensity. However, forecasting hurricane structure and intensity change is still a real challenge, especially when storm moving over the complex ocean features, such as the Gulf Stream and warm ocean eddies, which can result in a rapid intensification in some hurricanes under a favorable atmospheric environment. Uncertainty remains to be high from storm to storm. A lack of understanding of the mechanisms of how these ocean features influence hurricane structure could be one of the reasons. To address this issue, a coupled atmospheric-wave-ocean model is adopted in this study to simulate the evolution of Hurricane Katrina (2005), which shows the rapid intensification when moving into the Gulf of Mexico. The coupled model is consist of the 5th generation Pennsylvania State University / National Center for Atmospheric Research mesoscale model (MM5), WAVEWATCH III (WW3), and the 3D Price-Weller-Pinkel (3DPWP) upper ocean model. To examine the influence of the Loop Current and warm eddy on Katrina, coupled modeling experiments were conducted with both a simplified and a more realistic upper-ocean initial condition. The latter is based on the full physics Hybrid Coordinate Ocean Model (HYCOM) assimilation fields at 0000UTC 26 August 2005. Furthermore, experiments with and without WW3 are also compared to highlight the influence of the ocean surface waves on hurricane structure and intensity. Preliminary results show that both the surface waves and a better oceanic initial condition improved significantly the storm intensity forecasts compared to the observations. The inclusion of surface waves seems to produce a better wind-pressure relationship. To fully understand the physical processes that affect the hurricane intensity by oceanic initial condition and the surface waves, a comprehensive analysis of the storm structure, such as the eyewall evolution and rain band distribution, in the coupled model experiments is underway.
DE: 3300 ATMOSPHERIC PROCESSES
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting