Because there is more than one group carrying out weather predictions, there are many computer models used by meteorologists around the world. For example, the United States National Weather Service’s weather predictions are carried out at the National Centers for Environmental Prediction (NCEP). The NCEP runs several different computer models each day to determine the best weather forecasts. Some are used for short-term forecasting, others for the longer term; and some are used for global or hemispherical predictions, while others are only regional. They include the following mathematically intensive computer models (for more information about computer modeling, see , “Math in Computing”):

NGM—NGM, or the Nested Grid Model, is one in which observations are converted to values at various points that are evenly spaced, making it easy for computer programs to plug them into equations. This model is now considered to be obsolete.

WRF—The WRF (Weather Research and Forecasting) computer program is used for forecasting and research, created through the efforts of the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Atmospheric Research (NCAR), along with more than 150 international organizations. A special version of the program is called the Hurricane Weather Research and Forecasting (HWRF) model.

AVN, MRF, and GSM—The AVN (Aviation Model), MRF (Medium Range Forecast), and the GSM (Global Spectral Model) convert data into a large number of mathematical waves; they then return the waves in a manner that will produce a forecast map.

GFS—The GFS (Global Forecast System) is a global numerical weather prediction computer model run by the National Oceanic and Atmospheric Administration (NOAA); it was upgraded in 2010 by the National Centers for Environmental Prediction (NCEP). It produces high resolution forecasts—the first part of the model representing up to 180 hours (seven days), the second part of the model up to 16 days in advance (beyond seven days is often thought to be the limit of weather prognostication). It depicts several types of weather phenomena, such as precipitation types, precipitation movements, temperature, and winds.

RR—The RR (Rapid Refresh) is the next generation of hourly updated replacement information for the RUC (Rapid Update Cycle) model. It was developed for users who needed frequently updated, short-range weather forecasts, especially those working in the aviation field and in severe weather forecasting facilities.

ECMWF—The ECMWF (European Center for Medium-Range Weather Forecasts) is considered to be one of the most advanced weather forecast models in the world; it is mostly used for the Northern Hemisphere.

UKMET—The UKMET (United Kingdom meteorology offices) model also gives forecasts for the entire Northern Hemisphere.

MM5—The MM5 (Mesoscale Model #5) and WRF (Weather Research Forecast model) are actually the same models. The MM5 has long been a research computer model for smaller geographic forecast regions (such as Antarctica); the WRF is the name for MM5 as an operational model—not just for research.