Study on radar data assimilation for improving hurricane intensity and structure forecasts

Accurate predictions of hurricane intensity and structures at or near landfalls are of vital importance for hurricane preparation and damage mitigation; yet they continue to present a challenge for the hurricane and NWP communities. This is, in part, due to the rapid changes in hurricane intensity and structures during landfall caused by the multi-scale dynamical and physical interactions in the hurricane core regions and outside spiral rainbands and also by the sudden change of the surface conditions. In this study, we examine the possibility and capability of improving the short term prediction of hurricane intensity and structures near landfall by assimilating high-resolution, three-dimensional radar observations from radars in the landfall regions into a mesoscale NWP model. The landfall of Hurricane Isabel on the East Coast of US in 2003 is the focus of this study. Observations of Doppler radial velocity and reflectivity from five radars in the landfall region were collected and assimilated into the Navy's Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) in a variational data assimilation framework. Positive impacts of radar data assimilation on hurricane intensity and structure forecasts have been seen in the Isabel simulations. The detailed results from our recent study will be presented at the conference along with discussions on several issues including the impact of radar data coverage on hurricane forecasts.