Effects of cloud microphysical processes on hurricane intensification: WRF simulations of Hurricane Dennis (2005)

While improvements in hurricane models have resulted in better predictions of hurricane path, corresponding improvements in predicting the timing and degree of intensification have not been realized. One possible reason for this lack of improvement is a poor understanding of the impacts that cloud-scale processes have on the horizontal and vertical distributions of latent heating, the subsequent updraft and downdraft structure and the related feedbacks on hurricane intensity. The current study utilizes the Weather Research and Forecasting model (WRF) to improve our understanding of cloud microphysical processes in hurricane genesis and intensification. WRF is used with a movable, 1 km innermost grid to simulate Hurricane Dennis (2005), which was observed during the Tropical Cloud Systems and Processes (TCSP) field campaign in July, 2005, at times when Dennis was a tropical storm, as it transitioned from tropical storm to category 1 hurricane and as a category 2 storm. The simulations utilize the Ferrier microphysics scheme and are initialized with National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) data in the early stages of storm development. The simulations cover the time from 4 July 0000 UTC to 10 July 0000Z, during which Dennis evolved from a tropical depression to a category 4 hurricane. Advanced Microwave Precipitation Radiometer (AMPR) and radar data collected during TCSP on three separate days over Hurricane Dennis offer a unique set of remotely retrieved cloud and precipitation properties. Frequency diagrams of simulated brightness temperature, contoured frequency by altitude diagrams (CFADs) of equivalent reflectivity and Doppler velocity are used to evaluate how well the model can capture changes in cloud properties during three different stages of intensification.