A major upgrade to the ECMWF seasonal forecasting system has been made operational. The ECMWF seasonal forecasting system is upgraded relatively infrequently, to allow for extensive calibration and to provide stability for users. This month sees "System 4" become operational, providing both raw numerical data and graphical output to users.
The new system is at higher resolution (80km grid), represents the full stratosphere as well as the troposphere, the ocean and the land surface, and utilizes a slightly larger ensemble (51 members) and longer calibration period (30 years) than the previous system. Also, products are now released one week earlier than before, on the 8th of the month for restricted products and on the 15th for public products. Further details of the changes are available, as is a User Guide.
ECMWF is a WMO designated "Global Producing Centre" of seasonal forecasts, and uses its expertise in numerical modelling and data assimilation to produce some of the best available numerical calculations of expected seasonal weather patterns. Some limited graphical representations of the forecasts are made publicly available on the web, presently restricted to the tropics where forecast skill tends to be highest. The quality of the "El Nino" forecasts, for example for the NINO3.4 SST index in the eastern Tropical Pacific, is particularly well established.
The data from the ECWMF calculations are passed to National Meteorological Services and other providers, who use the model calculations and other available sources of data to produce forecast statements or products targetted for the general public and/or other user groups, such as government or the energy sector.
The ensemble mean 2 metre temperature anomaly for DJF 2011/12, predicted by the new ECMWF seasonal forecasting system (upper panel). The lower panel shows the corresponding skill of the forecast system, measured from tests for the period 1981-2010. Other plots including probability information and more information on skill are available on the web, with a public release at 12 UTC on the 15th of each month.