The NCEP North American Mesoscale Modeling System: Final Eta model/analysis changes and preliminary experiments using the WRF-NMM

NCEP has completed the final set of changes to the Eta model/analysis component of the North American Mesoscale (NAM, formerly Eta) modeling system and plans to implement them into production in the spring of 2005. Modifications to the NAM data assimilation system include the analysis of surface temperature observations over land, use of NEXRAD Level 2.5 radial winds, and adjustments to the assimilation of observed precipitation. Eta model changes include modifications to the cloud cover formulation in the radiation physics and improved land-surface physics. Details on these changes and their impact on NAM forecasts will be presented.

In the spring of 2006, NCEP plans to change the NAM system, replacing the Eta forecast model with the WRF Non-hydrostatic Mesoscale Model (NMM) and replacing the Eta 3DVAR analysis with the Grid-point Statistical Interpolation (GSI) analysis. Preliminary results from parallel runs over the North American domain and future plans with this system will be presented.