The fifth generation of the ECMWF seasonal forecasting system, in short SEAS5, will be introduced in the autumn of 2017, replacing System 4, which was released in 2011.
SEAS5 includes updated versions of the atmospheric (IFS) and interactive ocean (NEMO) models and adds the interactive sea ice model LIM2. The IFS uses a new grid and horizontal resolution has been increased (details below). Ocean horizontal and vertical resolution have also been increased. Ocean and land initial conditions have been updated, and the re-forecast ensemble size has been increased from 15 to 25. While re-forecasts span 1981 to 2016, the re-forecast period used to calibrate the forecasts when creating products will use the more recent period 1993 to 2016. SEAS5 highlights include a marked improvement in SST drift, especially in the tropical Pacific, and improvements in the prediction skill of Arctic sea ice.
For more detailed information and timetable visit Implementation of Seasonal Forecast SEAS5