North American Mesoscale Forecast System

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North American Mesoscale (NAM) Forecast System

The North American Mesoscale Forecast System (NAM) is one of the National Centers For Environmental Prediction’s (NCEP) major models for producing weather forecasts. NAM generates multiple grids (or domains) of weather forecasts over the North American continent at various horizontal resolutions. Each grid contains data for dozens of weather parameters, including temperature, precipitation, lightning, and turbulent kinetic energy. NAM uses additional numerical weather models to generate high-resolution forecasts over fixed regions, and occasionally to follow significant weather events like hurricanes.

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NAM Analyses

NAM Analysis Data

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

NAM Forecasts

NAM Forecast Data

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

Product History

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 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.

NCEP changed this model’s name from Meso-ETA to NAM in January 2005. NCEI/NOMADS servers incorporated this change on February 15, 2005.

Resources

Visit the NCEP-NAM home page for more information about how the model is configured and run, and to access forecast products.

• NCEP NAM Home Page
• WMO Headers for NCEP AWIPS NAM Products made available to NOAAPORT

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

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