Comparing Radar-Observed Hurricane Inner-Core Structure with that from Model-Prediction with and without Radar Data Assimilation

High-resolution airborn-radar reflectivity and radial velocity observations within the core of Hurricane Guillermo (1997) are employed first to verify and then to modify the inner-core structure of the model-predicted storm. The 4D-Var BDA scheme assimilating a bogus sea-level pressure is modified to alleviate the spin-up problem of TC initialization, allowing a reasonably realistic vortex size be maintained during the first few hours of a model forecast. The model-predicted vortex is comparable in size to radar observations after the modified BDA scheme is implemented. Moreover, the flow pattern and structures of the simulated reflectivity within the storm compared favorably to that of radar observations. However, the modeled storm is stronger in intensity than observed one and it deepened earlier than observations. The simulated reflectivity is larger in magnitude than radar observations, especially in the upper troposphere. Numerical results of forecast verification and data assimilation using radar observations at 2-4 km horizontal resolution are obtained and will be presented at the conference.