Skip Navigation Links
NOAA logo - Click to go to the NOAA homepage National Weather Service NWS logo - Click to go to the NWS homepage
EMC Logo
Navigation Bar Left Cap Home News Organization
Navigation Bar End Cap

         MISSION / VISION    |    About EMC


The North American Mesoscale Forecast System (NAM) is one of the primary vehicles by which NCEP's Environmental Modeling Center provides mesoscale guidance to public and private sector meteorologists. It is run four times daily at 00z, 06z, 12z, and 18z and consists of the following components:

- The NOAA Environmental Modeling System (NEMS) version of the Non-Hydrostatic Multi-scale Model in B-grid (NMMB)

- The NCEP regional Grid-Point Statistical Interpolation (GSI) analysis

The NAM is initialized with a 12-h run of the NAM Data Assimilation System, which runs a sequence of four GSI analyses and 3-h NEMS-NMMB forecasts using all available observations to provide a first guess to the NAM "on-time" analysis.

The NCEP High-Resolution Window Forecast System (HIRESW) consists of daily runs of the NEMS Non-hydrostatic Multiscale Model on B-grid (NEMS-NMMB) and the NCAR Advanced Research WRF (ARW) at ~3-4 km resolution. Initial conditions are provided by the NCEP Global Forecast System (GFS) for the Alaska, Hawaii, Puerto Rico, and Guam domains. The Rapid Refresh (RAP) analysis initializes the CONUS domain.

Currently, five nested domains are being run, two large domains (CONUS, Alaska) and three small domains (Hawaii, Puerto Rico, Guam). This is the current schedule:

0000Z : CONUS, Hawaii, Guam

0600Z : Alaska, Puerto Rico

1200Z : CONUS, Hawaii, Guam

1800Z : Alaska, Puerto Rico

IMPORTANT NOTE : As of 9/19/2013, preemption of the HIRESW run by the NCEP hurricane model runs has been suspended until further notice.

Additional NAM/HIRESW Information


Please mail comments, questions, suggestions about the Mesoscale Modeling Branch to Geoff DiMego, Branch Chief, at