Hurricane WRF model sensitivity to microphysics and radiation parameterizations

The Hurricane Weather Research and Forecasting (HWRF) model provides operational guidance to forecasters at the National Hurricane Center (NHC). It uses 27/9/3 km horizontal grid spacing, along with ocean coupling, hybrid ensemble-variational data assimilation, and vortex initialization. It is important that the HWRF model employ the best-performing physics schemes, so that it can provide superior representation of the large-scale environment and of the storm's inner core. The 2013 operational HWRF physics suite is comprised of the Ferrier microphysics parameterization and the Geophysical Fluid Dynamics Laboratory (GFDL) radiation scheme, along with other parameterizations suitable for hurricane conditions. The latest public release of HWRF, version 3.5a, provides the experimental capability to use the Thompson et al. (2008) microphysics parameterization. The Thompson and Ferrier microphysics schemes differ in a variety of aspects, including number of hydrometeor categories, existence of double-moment capability, choice of variables for advection, and algorithms for describing microphysics processes.. In addition, HWRF v3.5a contains a revised version of the Rapid Radiative Transfer Model originally developed for General Circulation Models (RRTMG). This scheme is coupled to the Thompson microphysics through direct calculation of the effective radii of cloud water, cloud ice, and snow, and their direct use in the computation of cloud optical depth. The Developmental Testbed Center (DTC) has conducted extensive tests of HWRF with Thompson microphysics and RRTMG radiation, and compared the results against those obtained using the operational physics suite. Results from the 2012 North Atlantic basin show improvement in track forecasts. However, the intensity errors are mixed. In this presentation, a diagnostic evaluation of these results, including a comparison of HWRF forecasts against reference analyses using the Model Evaluation Tools (MET), will be presented.