The fifth-generation mesoscale meteorological model (called MM5) is a regional nonhydrostatic, terrain-following, sigma-coordinate weather model developed jointly by the National Center for Atmospheric Research (NCAR) and Pennsylvania State University (PSU) (Dudhia et al. 2003). This model was developed originally by Anthes and his colleagues at PSU in the early 1970’s (Anthes and Warner 1978) and modified by NCAR/PSU modelers to include a multiple-nesting capability, nonhydrostatic dynamics, and four-dimensional data assimilation capability (Grell et al. 1995). The MM5 has been widely used for local weather forecasting, and has recently come to the attention of the coastal ocean modeling community who want to have accurate sea surface boundary forcing fields to drive forecast, nowcast, or hindcast coastal ocean models for both practical and scientific applications.

In the hindcast application, MM5 is initialized using the re-analysis NCEP (with a horizontal resolution of 2.5 degrees) or NCEP’s ETA (40-km resolution) databases with a preference for the latter when it was available. In the forecast application, MM5 is initialized using the forecast field from ETA. The hindcast or forecast meteorological fields are produced through the nested "two-way interaction" approach by running the model simultaneously on regional (27 km), local (9 km) and estuarine (3 km) domains. A four-dimensional nudging data assimilation is used to merge the model-predicted physical variables and parameters to the real-time observations taken by aircraft, weather balloons, satellite, and the network of land stations. Analysis nudging is applied to the regional doman and observational nudging for local domain.

The model was run for an integration period of every 5 days with 12 hours of model spin-up time. The initial and boundary conditions for a 5-day run are specified using the re-analysis NCEP or ETA databases or the forecast field from ETA. The time step used in integration was 90 sec for the regional domain, 30 sec for the local domain and 10 sec for the estuarine domain.  

The model output include 1) the surface wind stress, 2) air pressure, 3) heat fluxes (shortwave radiation, longwave radiation, sensible heat flux, and latent heat flux), and 4) precipiation/evaporation. These output data are linearly interpolated into the unstructured grids to drive the Satilla River FVCOM.