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The HWRF model runs on-demand with input provided by the National Hurricane Center (NHC), Central Pacific Hurricane Center (CPHC), and/or Joint Typhoon Warning Center (JTWC). HWRF consists of multiple movable two-way interactive nested grids that follow the projected path of a tropical system. The atmospheric component of the HWRF model was coupled to the Princeton Ocean Model (POM) for North Atlantic (NATL), Eastern Pacific (EPAC), and Central Pacific (CPAC) storms, and to the HYbrid Coordinate Ocean Model (HYCOM) for Western Pacific (WPAC) and North Indian Ocean (NIO) storms. Also, one-way coupling to wave model (Wave Watch III) was enabled for NATL, EPAC, and CPAC storms with hurricane surface wave products generated for these three basins. This means the HWRF grib filter will only update when there are active tropical systems in these three basins.

A sophisticated coupler was 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.

The model is run four times a day: 00Z, 06Z, 12Z, and 18Z. Each run produces forecasts of every 3 hours from the initial time out to 126 hours for a maximum number of 8 storms per cycle.