Global-scale seasonal forecasts, including those of precipitation and surface temperature, are routinely produced by WMO-accredited centres using sophisticated atmosphere-ocean coupled models, which take into account ENSO as well as other climate drivers. There are now 13 WMO Global Producing Centres of Long Range Forecasts, whose products are consolidated by a Lead Centre of Long Range Forecast Multi Model Ensemble
The update is intended as guidance for RCCs, Regional Climate Outlook Forums (RCOFs) and National Meteorological and Hydrological Services (NMHSs). It does not constitute an official forecast for any region or nation. Seasonal outlooks for any region or nation should be obtained from the relevant RCCs (see below for contact details) or NMHS.
Seasonal forecasts are probabilistic in nature. Although the text and figures used in the GSCU highlight the tercile categories that is predicted with the highest probability, it is important to recognize that the other tercile categories may also have substantial (though lower) probability.
The geographical areas occupied by the forecast signals should not be considered precise. Similarly, signals with small spatial extent may be unreliable.
The skill of seasonal forecasts is substantially lower than that of weather timescales and skill may vary considerably with region and season. It is important to view the forecast maps together with the skill maps provided in the supplementary appendices.