NWW3 implementations

The NOAA WAVEWATCH III^® operational wave model suite consists of a set of five wave models, based on version 2.22 of WAVEWATCH III^®. All models use the default settings of WAVEWATCH III^® unless specified differently.

• The global NWW3 model
• The regional Alaskan Waters (AKW) model
• The regional Western North Atlantic (WNA) model
• The regional North Atlantic Hurricane (NAH) model
• The regional Eastern North Pacific (ENP) model
• The regional North Pacific Hurricane (NPH) model

All regional models obtain hourly boundary data from the global model. All models are run on the 00z, 06z, 12z and 18z model cycles, and start with a 6h hindcast to assure continuity of swell. All models provides 126 hour forecasts, with the exception of the NAH model (72 hour forecast). No wave data assimilation is performed. All models are based on shallow water physics without mean currents. Additional model information is provided in the table and bullets below. The four time steps are the global step, propagation step for longest wave, refraction step and minimum source term step.

Model input:

• Winds from the operational Global Data Assimilation Scheme (GDAS) and the aviation cycle of the Medium Range Forecast model (Kanamitsu 1989, Kanamitsu et al. 1991, Derber et al., 1991, Caplan et al., 1997). This forecast/analysis system is now called the Global Forecast System or GFS. The winds are converted to 10m height assuming neutral stability. The wind fields are available at 3h intervals (using analyses and 3h forecasts in the hindcast part of the wave model run)
• For the NAH and NPH models, the above wind fields are blended with GFDL hurricane winds when possible. These wind fields are available hourly
• Ice concentrations are obtained from NCEP's automated passive microwave sea ice concentration analysis (Grumbine 1996) and are updated daily
• Sea Surface Temperatures as needed in the stability correction for wave growth are obtained taken from the GDAS
• Boundary data for the regional models are obtained from the global model and are updated hourly

Model output:

• Graphical and binary model output is available (see products page)

Bathymetry and obstruction grids:

• Operational wave models use a combination of bathymetric and obstruction grids.
• Bathymetric grid files contain an array of water depth values or land flags (zero depth) at the wave model resolution.
• Obstruction grids consist of two arrays representing the degree of meridional and zonal blocking of wave energy propagation due to subgrid topographic features (Tolman, 2003a).
• The table below provides links to grid preprocessor input files, bathymetric and obstruction grids used operationally at NCEP.

• Note that the NAH and NPH models use the same bathymetry and obstructions grids used in the WNA and ENP models, respectively.