Sensitivity of tropical cyclone forecasts using Grell-Frietas scheme with Hurricane WRF model

The Hurricane Weather Research and Forecasting (HWRF) model is a fully coupled atmosphere-ocean model run operationally for all global basins. HWRF is a complex multicomponent system, consisting of the Weather Research and Forecasting (WRF) atmospheric model coupled to the Princeton Ocean Model for Tropical Cyclones (MPIPOM-TC), a sophisticated initialization package including a data assimilation system and a set of postprocessing and vortex tracking tools. In recent years, the hurricane community has invested a substantial amount of effort to investigate and improve the representation of physical processes in the HWRF model. The Developmental Testbed Center (DTC) has partnered with the NOAA/NCEP Environmental Modeling Center (EMC) Hurricane Team and physics developers to evaluate innovative HWRF physical parameterizations directed at improving HWRF forecast skill. DTC is testing HWRF with an updated scale aware Grell-Frietas (GF) cumulus scheme and comparing them with the operational Scale-Aware SAS (SASAS) scheme. For this evaluation, retrospective HWRF forecasts for several storms in the Atlantic and Eastern Pacific basins were produced. Assessments are being done through a combination of physical process diagnostics as well as traditional track and intensity verification, including statistical significance. Preliminary results suggest improvement of track and intensity for the GF scheme compared to SASAS scheme. The GF was able to alleviate some of the negative intensity biases for intense storms. Results show that precipitation was higher from the microphysics scheme using GF scheme. Additionally, evaluation of large-scale and storm scale fields will be explored to further investigate sensitivities to the GF scheme in HWRF.