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Numerical Weather Prediction

An animated image of NAM simulated radar reflectivities

An animated image of NAM simulated radar reflectivities, forecast from 0000 UTC on July 10, 2012, to July 13, 2012, at 1200 UTC—a three and a half day forecast—in three-hourly intervals. 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 and ImageMagick.

Numerical Weather Prediction (NWP) data are the form of weather model data we are most familiar with on a day-to-day basis. NWP focuses on taking current observations of weather and processing these data with computer models to forecast the future state of weather. Knowing the current state of the weather is just as important as the numerical computer models processing the data. Current weather observations serve as input to the numerical computer models through a process known as data assimilation to produce outputs of temperature, precipitation, and hundreds of other meteorological elements from the oceans to the top of the atmosphere.

The following NWP data, and assimilation data (input observational weather data), are available through NOAA's National Operational Model Archive and Distribution System (NOMADS).

  • Global Data Assimilation System (GDAS)
    GDAS is the set of assimilation data, both input and output, in various formats for the Global Forecast System model.
  • Global Ensemble Forecast System (GEFS)
    GEFS is a global-coverage weather forecast model made up of 21 separate forecasts, or ensemble members, used to quantify the amount of uncertainty in a forecast. GEFS produces output four times a day with weather forecasts going out to 16 days.
  • Global Forecast System (GFS)
    The GFS model is a coupled weather forecast model, composed of four separate models that work together to provide an accurate picture of weather conditions. GFS covers the entire globe down to a horizontal resolution of 28 km.
  • Climate Forecast System (CFS)​
    CFS provides an operational, seasonal forecast of weather out to nine months.
  • North American Mesoscale (NAM)
    NAM is a regional weather forecast model covering North America down to a horizontal resolution of 12 km. Dozens of weather parameters are available from the NAM grids, from temperature and precipitation to lightning and turbulent kinetic energy.
  • Rapid Refresh (RAP)
    RAP is a regional weather forecast model of North America with separate sub-grids (with different horizontal resolutions) within the overall North America domain. RAP generates forecasts every hour with forecast lengths going out 18 hours. RAP replaced the Rapid Update Cycle (RUC) model on May 1, 2012.
  • Navy Operational Global Atmospheric Prediction System (NOGAPS)
    NOGAPS analysis data are available in six-hourly increments on regularly spaced latitude-longitude grids at 1-degree and one-half-degree resolutions. Vertical resolution varies from 18 to 28 pressure levels, 34 sea level depths, the surface, and other various levels.