Numerical Studies of Lower Boundary Forcing on Tropical Storm Fay (2008) over Southern Florida

This study is aimed to investigate the track and intensity changes of Tropical Storm Fay as it moved across south Florida. The maximum wind speed was achieved around 1800 UTC 19 August when the center was near the western side of the Lake Okeechobee. Observational data from the Florida wet season and monthly station reports around Lake Okeechobee (e.g., Clewiston, Belle Glade, and Immokalee) were analyzed. The overages of precipitation in the days before landfall left the soil moisture saturated ahead of Fay. Yet, the warmer SST over the lake as well as the west coast of Florida may have played a role to keep the intensity of the storm. It is our working hypothesis that the storm moved near Lake Okeechobee an intensified or closely held its intensity due to high soil moisture, and warmer SST over Lake Okeechobee and the west coast of Florida.

In order to examine our hypothesis, the simulations are performed using the Weather Research and Forecasting (WRF) model with 4 km and 1 km nested domains. The NAM 218 and the twelfth-degree RTG_SST analysis are adopted as the forcing data. The preliminary results demonstrate that the high-resolution simulation is able to recapture the track and deepening rate of the storm while passing through south Florida. The sensitivity experiments of land use and SST in this case will be performed to further illustrate its impacts on the intensity and track of Tropical Storm Fay during and after landfall.