Summary of available data

Release dates:
ECMWF:  on the 6th of each month at 12UTC
All other forecast systems:  on the 10th of each month at 12UTC

*
Currently these data are temporarily only available using CDS API and may appear as (partially or totally) unavailable in the CDS interactive forms.

Detailed information about the dates available as hindcasts or real-time forecasts for each individual forecast system can be found in Start dates available in the CDS per forecast system

For systems with lagged ensembles having multiple start dates, the "nominal" start date is assigned as follows:

Météo-France (all systems):

• Forecasts/Hindcasts: nominal month M includes the members initialised in the last weeks of month M-1 and on the 1st of month M

NOTE: Even though the different members of all Météo-France forecasting system ensembles are initialized using a lagged approach, the real start dates are not revealed to the users, so all members are encoded as if they were initialized on the 1st of the month

UK MetOffice (all systems):

• Forecasts: nominal month M includes the members initialised on the 1st of month M and all available members with start dates back to, and including, the 2nd of month M-1
  • Note that even though just the most recent 50 members are used for C3S products, the complete set of members are available through the CDS
• Hindcasts: nominal month M includes the members initialised on the 1st of month M and on the 25th, 17th and 9th of month M-1

NCEP:

• Forecasts: nominal month M includes the members initialised on the 1st of month M and all available members with start dates back to, and including, the 2nd of month M-1
  • Note that even though just the most recent 52 members are used for C3S products, the complete set of members are available through the CDS
• Hindcasts: nominal month M includes the members initialised on the 1st of month M (if available) and on all start days from month M-1 except the 1st (see table below)

JMA:

• Forecasts: nominal month M includes the members initialised on the 1st of month M (if available) and on all start days from month M-1 except the 1st
  • Note that even though only a subset using the most recent members is used for C3S products, the complete set of members is available through the CDS
    • For CPS2 the subset includes 52 members (4 start dates)
    • For CPS3 the subset includes 55 members (11 start dates)
• Hindcasts: nominal month M includes the members initialised on the 2 available start dates from month M-1

See details about available dates from JMA at section 6 (Other relevant information) of the forecasting system description.

Bureau of Meteorology:

• Forecasts: nominal month M includes the members initialised on the 1st of month M and on the last 10 days of month M-1
  • Note that even though just the most recent 55 members are used for C3S products, the complete set of members are available through the CDS
• Hindcasts: nominal month M includes the members initialised on the 1st of month M and on the last 8 days of month M-1
  • Note that for nominal March, both non-leap years and leap years use the same 8 days of February (i.e. 29th February on leap years is not used)

_{This document has been produced in the context of the Copernicus Climate Change Service (C3S).}

_{The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Delegation agreement signed on 11/11/2014). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose.}

_{The users thereof use the information at their sole risk and liability. For the avoidance of all doubt, the European Commission and the European Centre for Medium-Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view.}