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Currently, there are graphical products available in the C3S web site and public access to the data is provided via the ECMWF WebAPI. From 2018 onwards, C3S seasonal forecast data products will be made available via the C3S Climate C3S Climate Data Store (CDS).
Seasonal forecasts are not weather forecasts: the role of the hindcasts
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Every forecasting system that contributes to C3S will have a different lifetime, so different versions of the systems are expected to be changed, upgraded from their original institutions. For the real-time forecasts just one version of each one of the contributors will be made available to C3S as a real-time forecasts. For instance, in November 2017 ECMWF has changed its operational seasonal forecasting system from system 4 to SEAS5, but both systems will be kept routinely running in parallel at ECMWF for a while. Despite that fact, the only version of ECMWF seasonal forecasts available at C3S from November 2017 onwards will be SEAS5.
NOTE: In the current data service based on web-API access to the MARS archive, where the data is stored using the GRIB format, those version changes are tracked using the MARS keyword "SYSTEM" included in every GRIB field.
How the seasonal forecasting systems build their ensembles? And how data are produced?
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(a) Despite they are produced in a lagged mode, the data from MeteoFrance system5 is produced and archived provided at CDS as if all the members were initialized on the 1st
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