NCEP/EMC HWRF for Global TCs

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The HWRF system is composed of the WRF model software infrastructure, the Non-Hydrostatic Mesoscale Model (NMM) dynamic core, the three-dimensional Princeton Ocean Model (POM), the NCEP coupler, and a physics suite tailored to the tropics, including air-sea interactions over warm water and under high wind conditions, and boundary layer and cloud physics developed for hurricane forecasts. The atmosphere-ocean coupled HWRF system consists of multiple movable two-way interactive nested grids that follow the projected path of the storm. Atmospheric component of the HWRF model was coupled to the Princeton Ocean Model (POM) developed by GFDL/URI using a sophisticated coupler developed at NCEP for providing accurate representation of air-sea interactions. An advanced vortex initialization scheme and NCEP GSI based HWRF Data Assimilation System (HDAS) provide means to represent the initial location, intensity, size and structure of the inner core of a hurricane and it’s large-scale environment. The NCEP Global Forecast System (GFS) analysis and forecasts provide initial and boundary conditions for the HWRF model. POM uses a feature based initialization procedure for representing oceanic features such as the loop current, warm/cold core rings and the cold wake generated by the storm.

Before HWRF becoming operational at NCEP in 2007, and it has been developed at EMC since 2002, in collaboration with NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) scientists and the University of Rhode Island (URI) as well as other teams shown in the Colloborators tab. To meet operational implementation requirements, it was necessary that the skill of the track forecasts from the HWRF and GFDL hurricane models be comparable. Additionally, features of the GFDL hurricane model that led to demonstrated skill for intensity forecasts, such as ocean coupling, upgraded air-sea physics and improvements to microphysics, were also captured in the newly developed HWRF system.

As a major step towards providing improved intensity forecast skill, for 2012 hurricane season, the operational HWRF model was configured with triple-nest capability that includes a cloud-resolving inner most grid operating at 3 km horizontal resolution, encompassed by an intermediate grid at 9 km resolution and the outer domain at 27 km resolution. Further enhancements to the HWRF model resulted in major upgrades for 2013 hurricane season that included more sophisticated nesting techniques and one-way hybrid regional data assimilation system with real-time ingestion of NOAA P3 Tail Doppler Radar data. For the first time, operational HWRF model has shown intensity forecast skill superior to that of NHC Official forecasts as well as best performing statistical models. HWRF track skills were shown comparable to the best performing NCEP GFS model for both ATL and EPAC basins. FY13 version of HWRF was also coupled, for the first time, to the 1-D POM model in the EPAC basin. In 2014, the EMC hurricane team succeeded in making further improvements to the HWRF model by implementing another set of major upgrades to both the atmospheric and ocean model components along with several product enhancements. The FY14 configuration of HWRF model had increased vertical resolution from 42 to 61 levels, and was coupled to a unified Message Passing Interface Princeton Ocean Model (MPI-POM) for the Atlantic basin including Gulf of Mexico and full 3D MPI-POM for the East Pacific basin. Product enhancements include 3-hr frequency of model output and a very high temporal resolution (5 seconds) information on location of the storm center and its intensity (HTCF). FY14 HWRF was able to demonstrate highest track forecasts skills in the Atlantic basin compared to any other operational model used at NHC, and also provided much improved intensity forecast guidance.

For more information on other hurricane models associated with EMC or the HWRF, please see the Collaborators tab.