Evaluating the impact of boundary layer parameterization on hurricane intensity and structure in HWRF forecasts

As part of the Hurricane Forecast Improvement Project (HFIP), the planetary boundary layer (PBL) parameterization scheme in the operational Hurricane Weather Research and Forecasting (HWRF) model has been recently modified based on previous turbulence observations. Zhang et al. (2015) documented the impact of reducing vertical eddy diffusivity on HWRF forecasts of storm track, intensity, and structure in comparison with observations. The impact of this PBL scheme improvement on hurricane rapid intensification forecasts in HWRF was evaluated by Zhang et al. (2017). How the parameterized boundary layer structure affects the hurricane rapid intensification and asymmetric structure in shear was investigated by Zhang and Rogers (2019). This talk first presents some key findings from these studies. Then the PBL schemes in all previous operational versions of the HWRF model are reviewed. The effect of these different PBL schemes on hurricane structure and intensity change is investigated using idealized HWRF simulations. Further improvement of the HWRF PBL scheme is discussed.