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North American Mesoscale Forecast System (NAM)

An animation of NAM total surface 3-hourly precipitation

An animated image of NAM total surface 3-hourly precipitation, forecast from 03 UTC on July 10, 2012, to July 13, 2012, at 12 UTC. In the initial few frames, hurricane Emilia can be seen in the bottom left corner spinning off to the west. This image was produced with the Grid Analysis and Display System (GrADS) and ImageMagick.

The North American Mesoscale Forecast System (NAM) is one of the major weather models run by the National Centers for Environmental Prediction (NCEP) for producing weather forecasts. Dozens of weather parameters are available from the NAM grids, from temperature and precipitation to lightning and turbulent kinetic energy. The NAM generates multiple grids (or domains) of weather forecasts over the North American continent at various horizontal resolutions. High-resolution forecasts are generated within the NAM using additional numerical weather models. These high-resolution forecast windows are generated over fixed regions and are occasionally run to follow significant weather events like hurricanes. The NAM home page is an excellent source of information for how the model is configured and run and an excellent source of forecast products.

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A plot of NAM data showing an analysis of mean sea level pressure on July 10, 2012, at 00 UTC

A plot of NAM data showing an analysis of mean sea level pressure on July 10, 2012, at 00 UTC. Low pressures are colored in red, higher pressures in blue. In the bottom left corner, the center of hurricane Emilia (a category 2 hurricane at this time) is visible as a red dot surrounded by an orange circle. Data contours were generated with the Grid Analysis and Display System (GrADS) and visualized with Quantum GIS (QGIS), an open-source Geographic Information System (GIS).

In January 2005, NCEP officially changed the name of this model from Meso-ETA to the North American Mesoscale Forecast System (NAM). The NOAA National Operational Model Archive and Distribution System (NOMADS) followed up with a name change from Meso-ETA to NAM on February 15, 2005.

As of June 20, 2006, the NAM model has been running with a non-hydrostatic version of the Weather Research and Forecasting (WRF) model at its core. This version of the NAM is also known as the NAM Non-hydrostatic Mesoscale Model (NAM-NMM). Between February 15, 2005, and June 20, 2006, NAM was run with the Meso-ETA model.

The analyses from all NAM and ETA runs are unified under the NAM-ANL product type.

Product Types

NAM Analyses

Model Grid/Scale Period of Record Model Cycle Output Timestep Data Access Links
NAM-ANL 218 (12km) - Domain 03Mar2004–Present 4/day: 00, 06, 12, 18UTC +00, (+03, +06 precipitation fields) Plot|FTP4u FTP HTTP GDS TDS HAS

NAM Forecasts

Model Grid/Scale Period of Record Model Cycle Output Timestep Data Access Links
NAM-NMM 218 (12km) - Domain 20Jun2006–Present 4/day: 00, 06, 12, 18UTC 3-hourly, +00 to +84 hours Plot|FTP4u FTP HTTP GDS TDS HAS
Meso-ETA 218 (12km) - Domain 15Feb2005–19Jun2006 4/day: 00, 06, 12, 18UTC 3-hourly, +00 to +84 hours Plot|FTP4u HAS
Meso-ETA 218 (12km) - Domain 01Mar2004–23Mar2005 4/day: 00, 06, 12, 18UTC 3-hourly, +00 to +84 hours Plot|FTP4u FTP HTTP HAS
Meso-ETA 215 (20km) - Domain 02Jun2003–25May2005 4/day: 00, 06, 12, 18UTC 3-hourly, +00 to +60 hours FTP HTTP
Meso-ETA 212 (40km) - Domain 02Jun2003–25May2005 4/day: 00, 06, 12, 18UTC 3-hourly, +00 to +60 hours FTP HTTP
Meso-ETA 211 (81km) - Domain 02Jun2003–25May2005 2/day: 00, 12UTC 6-hourly, +00 to +60 hours FTP HTTP
Early-ETA 212 (40km) - Domain 02Jun2003–25May2005 2/day: 00, 12UTC 3-hourly, +00 to +60 hours FTP HTTP

Data Usage Notes

July 2003: MSLET Missing for ETA 218 Forecast Hour 09

Messages from 09-hour forecast data for parameter MSLET in the ETA 218 grid are corrupt for all the cycles. We are unable to plot this data using GrADS or extract the data using GDS.

Also, the 09-hour forecast data for parameter MSLET in the ETA 218 grid is not being transmitted as a separate message. It is appended to the message for the forecast hour 03 data. It should arrive as bulletin ZPBE89*, but it arrives within bulletin ZPBB89*.

nomads3.ncdc.noaa.gov 54: wgrib -s ZPBB89_KWBE_20030710_0000
1:21:d=03071000:MSLET:MSL:3hr fcst:NAve=0
2:427172:d=03071000:MSLET:MSL:9hr fcst:NAve=0

Publication References

None

Miscellaneous Documentation

None

Links

GrADS PDEF files for the NOAAPort grids can be downloaded from our site. These files are needed for using locally downloaded copies of certain datasets in GrADS.

NCEP NAM Home Page

WMO Headers for NCEP AWIPS NAM Products made available to NOAAPORT