Long range forecasts provide information about expected future atmospheric and oceanic conditions, averaged over periods of one to three months. Like the medium and extended ranges, the long range forecasts are produced by the IFS coupled ocean-atmosphere model. Long term predictions rely on aspects of Earth system variability which have long time scales (months to years) and are, to a certain extent, predictable. The most important of these is the ENSO (El Nino Southern Oscillation) cycle. Although ENSO is a coupled ocean-atmosphere phenomenon centred over the tropical Pacific the influence of its fluctuations extends around the world. Many other sources of predictability are also represented by the forecast system.
Long range forecasts are released every month and extend seven months in the future. Annual range forecasts are produced with the same system every three months, and extend thirteen months in the future.
The fifth generation of the ECMWF seasonal forecasting system, SEAS5, was introduced in November 2017, replacing System 4. SEAS5 includes updated versions of the atmospheric (IFS) and ocean (NEMO) models and adds the interactive sea ice model LIM2.
SEAS5 data is contributed to the Copernicus Climate Change Service's multi-system seasonal forecast.
Please provide feedback on the SEAS5 user guide, so it can continue to be improved.
EUROSIP multi-model system
Please note that Products from the EUROSIP Multi-model Seasonal Forecasting System has been discontinued on October 2019.
The Copernicus Climate Change Service (C3S) has similar multi-model seasonal data available in the Climate Data Store.
ECMWF Seasonal forecast system operational history
Operational from November 2011 to October 2017
- System 4 user guide
- System 4 technical memorandum
- System 4 uses IFS cycle 36r4
- Operational from March 2007 to October 2011
- System 3 user guide
- System 3 article in Climate Dynamics
- System 3 technical memorandum
- Operational from to January 2002 to February 2007
- System 2 user guide
- Produced forecasts from January 1997 to December 2001
- System 1 user guide