High-Resolution Radar Data Assimilation for Hurricanes Near Landfalls

Accurate forecasting of a hurricane’s track and intensity changes near its landfall is of great importance in making an effective hurricane warning. This study examines the impact of radar data from both airborne Doppler radar and ground-based WSR-88Ds on numerical simulations of landfalling hurricanes.

First, the impact of airborne Doppler radar data on numerical simulation of Hurricane Sandy (2012) was conducted with the community mesoscale Weather Research and Forecasting (WRF) model and the NCEP GSI data assimilation system. Both radial velocity and radar reflectivity data were assimilated. Specifically, for radar reflectivity assimilation, the direct assimilation was compared with a cloud analysis initialization. It is found that the cloud analysis initialization outperforms the direct assimilation of radar reflectivity regarding the improvements in hurricane intensity simulation. Moreover, combining cloud analysis with radial velocity data assimilation leads the best impacts on hurricane track and intensity simulation.

Additional numerical experiments are conducted to examine the impact of WSR-88D ground-based radar data on the numerical simulation of Hurricane Charley (2004) near its landfall. With the axisymmetric wind fields, vertical velocity, tangential winds and reflectivity derived from the ground-based velocity track display (GBVTD) technique (Lee and Bell 2007), different data assimilation configurations are tested to identify the radar derived wind component that has the most impact on hurricane intensity forecasting.