Please note: Due to browser FTP deprecation, users will no longer be able to access NCEI data via browser FTP clients. Users may access data via NCEI Web Accessible Folders and/or FTP client supported applications. We apologize for any inconvenience. See this document as reference.

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.

More...

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	18May2020–Present online, since 03Mar2004 in archive	4/day: 00, 06, 12, 18UTC	+00, (+03, +06 precipitation fields)	HTTPS TDS AIRS
NAM-ANL, Historical	218 (12km) - Domain	03Mar2004–15May2020 online	4/day: 00, 06, 12, 18UTC	+00, (+03, +06 precipitation fields)	HTTPS TDS AIRS

NAM Forecasts

Model	Grid/Scale	Period of Record	Model Cycle	Output Timestep	Data Access Links
NAM-NMM	218 (12km) - Domain	31May2020–Present online, since 20Jun2006 in archive	4/day: 00, 06, 12, 18UTC	3-hourly, +00 to +84 hours	HTTPS TDS AIRS
NAM-NMM, Historical	218 (12km) - Domain	20Jun2019–15May2020 online	4/day: 00, 06, 12, 18UTC	3-hourly, +00 to +84 hours	HTTPS TDS AIRS
Meso-ETA	218 (12km) - Domain	15Feb2005–19Jun2006	4/day: 00, 06, 12, 18UTC	3-hourly, +00 to +84 hours	AIRS
Meso-ETA	218 (12km) - Domain	01Mar2004–23Mar2005	4/day: 00, 06, 12, 18UTC	3-hourly, +00 to +84 hours	AIRS
Meso-ETA	215 (20km) - Domain	02Jun2003–25May2005	4/day: 00, 06, 12, 18UTC	3-hourly, +00 to +60 hours	HTTPS
Meso-ETA	212 (40km) - Domain	02Jun2003–25May2005	4/day: 00, 06, 12, 18UTC	3-hourly, +00 to +60 hours	HTTPS
Meso-ETA	211 (81km) - Domain	02Jun2003–25May2005	2/day: 00, 12UTC	6-hourly, +00 to +60 hours	HTTPS
Early-ETA	212 (40km) - Domain	02Jun2003–25May2005	2/day: 00, 12UTC	3-hourly, +00 to +60 hours	HTTPS

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