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NATIONAL WEATHER ASSOCIATION


NEWS on NWP MODEL CHANGES

On 20 June 2006, the NOAA/NWS/National Centers for Environmental Prediction (NCEP) will replace the NCEP Eta model with the NCEP North American Mesoscale (NAM) Weather Research and Forecasting (WRF) Model. The NCEP Eta model has been the workhorse short-range forecast model used for forecast guidance over the United States for more than a decade. It is being replaced by the NCEP Nonhydrostatic Mesoscale Model (NMM), and its analysis is being replaced by the Gridpoint Statistical Interpolation (GSI). The NMM and GSI are running in the WRF infrastructure.

The COMET Program is pleased to announce the publication of two versions of the Webcast, "The NCEP North American Mesoscale (NAM) Weather Research and Forecasting (WRF) Model," in time for the replacement of the NCEP Eta  model by the new WRF model. The condensed version focuses on the most  practical information about the new model and analysis changes and has a
40-minute run time. The full version provides more in-depth explanations  of model changes and runs 75 minutes.

Each of the Webcasts highlights the major forecast impacts resulting from these changes and includes the following content:
  • An introduction to WRF concept
  • Basic discussion of how GSI improves the analysis, including
  • Conceptual explanation of anisotropic background error covariances, which the GSI will first use in the Real-Time Mesoscale Analysis (RTMA) and later in the NAM-WRF
  • Information on differences between the vertical coordinate systems in Eta and NMM and how they affect the forecast
  • Discussion of nonhydrostatic effects, including a case example
  • Presentation of new output variables, including precipitation type and simulated radar reflectivity

The NCEP NAM WRF Model (Full Version) is available at:
http://www.meted.ucar.edu/nwp/NAMWRF/index.htm

The NCEP NAM WRF Model (Short Version) is available at:
http://www.meted.ucar.edu/nwp/NAMWRF_short/index.htm

COMET also has a web forum for discussing current NCEP model runs, including WRF
located at: http://www.meted.ucar.edu/metedbb/forums/list.page

The WRF runs are discussed on the NAM/mesoscale forum, and postings about any interesting, curious, or problematic aspects of the model forecasts as well as questions are highly encouraged.

These Webcasts are coded in Macromedia Flash 6.0 and require the Flash plug-in to hear the audio and view the animations. Internet Explorer will automatically install the required Flash Player ActiveX Control (if missing). The newest Netscape browsers typically include the Flash Player plug-in with the installation program. Mozilla/Firefox browsers do not distribute the Flash Player plug-in. If you need to install the plug-in, follow the directions on the Tech Notes page of the Webcast.