Recent results on landfalling hurricanes with the GFDL hurricane-land-ocean coupled system at NCEP

A comprehensive land surface model (namely the Noah LSM) that predicts both soil moisture and temperature for multiple layers has recently been integrated into the GFDL hurricane model at NCEP. The system has been extensively tested for both historical cases (back to 98) and the recent hurricane seasons. It was found that for near-landfall and short (3 days) time forecasts, the impacts of the Noah LSM coupling are generally minor in both intensity and track. However, the precipitation differences are more pronounced, implying the relative importance of land coupling in predicting inland rainfall and flooding. Our recent analysis on landfall precipitation (with resolution of 1/3 degree) indicates that the hurricane-Noah LSM coupled system in general improves the landfall precipitation forecast. Most recently, we found that the land surface coupling can considerably affect hurricane tracks for 5-day prediction over western Atlantic. Typically, an eastward moving high over northern America is slightly weakened after 3-4 days when moving into western Atlantic. This leads to earlier (relative to the operational) turn of hurricanes with the Noah LSM coupling. Nearly 40 cases were performed with this system for the major landfalling hurricanes for the season of 2005. The results indicate a slight overall improvement in hurricane track while the intensity remains nearly the same. Detailed statistics and precipitation verification will also be reported.