The NCEP Climate Forecast System version 2 (CFSv2) in raw form is run as a 4-member ensemble 4 times per day. Typically, this is turned into a time-lagged 16-member ensemble, i.e. today’s 00Z initialisations are combined with the 06, 12, and 18Z initialisations from yesterday.
Following the style used in the S2S database, the sub-seasonal stratosphere forecasts shown here run out to 44 days.
The 4-weekly 500 hPa anomalies use a 16-member ensemble (1 day, 4 runs of 4 members), while the 6-monthly 700 hPa anomalies use a 40-member ensemble (10 days of 4 members).
CFSv2 became operational in March 2011.