The second version of the National Centers for Environmental Prediction (NCEP)'s Climate Forecast System (CFSv2) was made operational at NCEP in March 2011. It is a fully coupled model representing the interaction between the Earth's atmosphere, oceans, land and sea-ice. For forecast products issued in May 2022 onwards, Copernicus C3S-NCEP data are used.
Forecasts: The NCEP CFSv2 forecasts are generated using ensembles of 50 members, or 50 model runs. As four model runs are available each day, the current practice is to use the latest 12/13 days’ forecast to the 1st of each month to build the ensemble for the nominal start date on the first of that month.
Re-forecasts: The re-forecast data are also used in the verification of the forecasts, as well as for creating the climatology. We use a re-forecast period of 1993-2016, with five to seven start days (4 model runs every 5 days day) made available depending on the calendar start month. Our current practice is to use all available start days' runs for each calendar month to create an ensemble of 20 to 28 members.
Further information on NCEP CFSv2 (C3S dataset) can be found in Copernicus Services link. More information on NCEP CFSv2 can also be found in Saha et al. 2014: