Doppler radar reflectivity data provide distributions of hydrometeors at a high spatial and temporal resolution. The data are very useful in depicting the realistic structure of microphysical properties of TC vortices. In this study, the airborne Doppler radar reflectivity data are assimilated into the mesoscale WRF model to improve the initial specification of cloud microphysical properties in the inner core of the Hurricane Dennis (2005). The impact of the data in representing cloud microphysical properties and convection distributions in the initial vortex is examined. High-resolution numerical simulations are then conducted with the improved initial conditions. By analyzing the model simulations, the impact of the radar reflectivity on the forecasts of the intensity, track, and the storm inner core dynamic and thermodynamic structures for Hurricane Dennis is investigated. The physical mechanisms through which the cloud microphysical processes influence TC intensity change are also discussed.