The North American Ensemble Forecast System (NAEFS) is a joint project involving the Meteorological Service of Canada (MSC) in Canada, the National Weather Service (NWS) in the United States, and the National Meteorological Service of Mexico (NMSM) in Mexico providing numerical weather prediction ensemble guidance for the 1- to 16-day forecast period.[1] The NAEFS combines the Canadian MSC (Global Environmental Multiscale Model) and the US NWS global ensemble prediction systems (Global Forecast System), improving probabilistic operational guidance over what can be built from any individual country's ensemble.[1] Model guidance from the NAEFS is incorporated into the forecasts of the respective national agencies.[2][3]
NAEFS operates on the fundamental principles of ensemble forecasting which provides a range of possible weather forecasts of the atmospheric state over a given forecast period. The initial state of the atmosphere and/or the numerical weather prediction model configuration are slightly varied to provide a range of possible forecast solutions.[4][5] The global ensemble prediction systems at MSC and NWS use slightly different, but equally valid methods to initialize and integrate the atmospheric state. By combining the ensembles from both centers into one ensemble, the possible range of future atmospheric states for a given forecast period are better sampled, producing on average, improved estimates of the future atmospheric state and the associated uncertainty.[6][7][8] NAEFS collaboration allows the national weather agencies to pool their research resources and make improvements to the ensemble prediction systems more quickly and efficiently. The exchange of knowledge allows research and operations to develop a new generation of ensemble products with the goal of improving timeliness and accuracy in alerting the public of high impact weather events.