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.
Upgrade to SEAS5
The fifth generation of the ECMWF seasonal forecasting system, SEAS5, will be introduced in November 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 table below summarizes the upgrades in model components and initialization for SEAS5.
|IFS horizontal resolution||TL255||TCO319|
|IFS Gaussian grid||N128 (80 km)||O320 (35 km)|
|IFS vertical resolution (TOA)||L91 (0.01 hPa)||L91 (0.01 hPa)|
|IFS model stochastic physics||3-lev SPPT and SPBS||3-lev SPPT and SPBS|
|Ocean horizontal resolution||ORCA 1.0||ORCA 0.25|
|Ocean vertical resolution||L42||L75|
|Sea ice model||Sampled climatology||LIM2|
|ERA-Interim land (36r4)/Operations||ERA-Interim land (43r1)/Operations|
|Forecast ensemble size|
|Re-forecast years||30 (1981-2010)||36 (1981-2016)|
|Re-forecast ensemble size|
- SEAS5 user guide
- Articles describing and assessing SEAS5 are in preparation for submission to peer-reviewed literature
- SEAS5 uses IFS cycle 43r1
EUROSIP multi-model system
The EUROSIP multi-model seasonal forecasting system consists of a number of independent coupled seasonal forecasting systems integrated into a common framework. From March 2017 the systems include those from ECMWF, the Met Office, Météo-France, NCEP and JMA.
For more information see the documentation of the EUROSIP system.
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