Study of the ocean role in intensity forecast for landfall hurricanes using coupled HYCOM-HWRF system

It has been observed that hurricanes traversing the Loop Current (LC) often resulted in greater devastation in the Gulf Coast than ones that avoided, for example Hurricane Katrina (12L) in 2005. A probable reason is that the oceanic thermal current might provide a favorable condition for hurricane intensification, owing to its deep mixed layer and a body of relatively warm water (≥26oC) above. The Loop Current is going through contraction and extension in latitude on a regular basis, probably related to eddy shedding process. During the extension period, the northern front can reach as far as the Mississippi River delta or the Florida Panhandle, hence containing potentially more available heat. A similar effect is expected for a warm core eddy, whereas the frontal eddies or shingles of the main LC current may cause negative feedback (Walker et al. 2009). We investigate the role of the LC in intensification using coupled Hurricane Weather Research and Forecast (HWRF) to HYbrid Coordinate Ocean Model (HYCOM) - HyHWRF. We focus on Hurricane Gustav (07L) and Ike (09L) in 2008. The study includes a relationship of the LC northern extent to intensification. Also investigated is storm-induced cooling during the passage over the margin of the LC, and its relation to intensification.