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The production of seasonal forecasts, also known as seasonal climate forecasts, have experienced has undergone a huge transformation in the last few decades: from a purely academic and research exercise in the early '90s to the current situation where several meteorological forecast services, throughout the world, conduct routine operational seasonal forecasting activities. Such activities are devoted to provide providing estimates of statistics of weather in on the seasonal and monthly time scales, and they lie in a place which places them somewhere between conventional weather forecasts and climate predictions.
In that sense, even though seasonal forecasts share some method methods and tools with weather forecasting, they are part of a different paradigm which requires treating them in a different waysway. Seasonal forecasts instead Instead of trying to answer to the question "how is the weather going to look like on a particular location in an specific day?", they seasonal forecasts will tell us how likely it is that the coming season will be wetter, drier, warmer or colder than the 'usual conditions ' for that time of year. This kind of long term predictions are feasible due to the behaviour of some of the earth Earth system components which evolve more slowly than the atmosphere (e.g. the ocean, the cryosphere) and in a predictable fashion, so their influence in on the earth system atmosphere can add a noticeable signal.
We consider here as seasonal forecasts data both the higher-frequency (sub-daily and daily) data outputs from numerical earth system weather or climate models and the derived monthly and seasonal products, up to a few months ahead of their initialization date.
Seasonal forecasting within the C3S
The C3S seasonal forecasting forecast products are based on data from several state-of-the-art seasonal prediction systems. Multi-system combinations, as well as predictions from the individual component participating systems, are available. The centres currently providing forecasts to C3S are ECMWF, The Met Office and Météo-France; in the coming months data produced by Deutscher Wetterdienst (DWD) and Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC) will be included in the C3S multi-system.
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