The Hurricane Weather Research and Forecasting model (HWRF) is a limited-area numerical model used by the National Weather Service (NWS) to provide numerical guidance for operational tropical cyclone forecasting. The atmospheric component of HWRF employs the Non-Hydrostatic Model (NMM) dynamic core of Weather Research and Forecasting (WRF) model. The oceanic component of HWRF is a parallelized version of the Princeton Ocean Model for Tropical Cyclones (MPIPOM-TC).

In order to facilitate the testing of recent physics advancements for HWRF, DTC partnered with the NOAA Environmental Modeling Center (EMC) to evaluate several physics innovations for the HWRF modeling system in preparation for the 2017 hurricane season. These innovations consisted of cloud-radiation advancements within the Rapid Radiative Transfer Model for Global Climate Models (RRTMG) radiation scheme, including a new cloud overlap methodology and modifications to the operational partial cloudiness scheme. Additionally, DTC evaluated an alternate configuration of HWRF using the Grell-Freitas cumulus parameterization.

For this test, the DTC ran retrospective forecasts for several storms during 2014-2016 seasons using four configurations of HWRF. The control (H6CL) configuration follows the HWRF 2016 operational implementation version. The H6CO configuration differs from H6CL in that an exponential-random (ER) cloud overlap method was applied rather than the default maximum-random (MR) method, whereas the H6PC configuration included modifications to the partial cloudiness (icloud=3) called in RRTMG by default in HWRF. The H6GF configuration used the Grell-Freitas cumulus parameterization in place of the operational scale-aware simplified Arakawa-Schubert (SAS).

Runs were conducted on the jet and theia NOAA research computers, where all four configurations were always run on the same platform for a given storm.

Contact information: Kathryn Newman, DTC Hurricane Task Lead (knewman@ucar.edu)