The Subseasonal-to-Seasonal Prediction Project

Subseasonal-to-Seasonal prediction project 

Many management decisions, for example in the context of agriculture, have to be taken on sub-monthly scales – a time scale that lies between the well-established and routine use of weather forecasts and the developing use of seasonal forecasts. Thus forecasts for the sub-monthly scale is of high interests to a variety of user groups. So far, forecasting for the sub-seasonal time range has received much less attention than medium-range and seasonal predictions, and has long been considered a “predictability desert.” However, recent research has indicated important potential sources of predictability for this time range, through better representation of atmospheric phenomena such as the Madden Julian Oscillation (MJO) and improved coupling with, and initialization of, the land-ocean cryosphere and stratosphere. Better understanding of these potential sources of predictability together with improvements in model development, data assimilation and computing resources should result in more accurate sub-seasonal forecasts.

The Subseasonal-to-Seasonal prediction project (S2S) started in 2013 as a collaborative structure set up by the World Climate Research Programme (WCRP) and the World Weather Research Programme (WWRP) to address the challenges of predictions on the sub-seasonal to seasonal time-scale. The project brings together the weather and climate research communities to leverage their expertise for improving predictions on the timescales of particular relevance to the Global Framework for Climate Services (GFCS).


  • To improve forecast skill and understanding on the sub-seasonal to seasonal timescale with special emphasis on high-impact weather events
  • To promote the uptake of results by operational centres and exploitation by the applications community
  • To capitalize on the expertise of the weather and climate research communities to address issues of importance to the Global Framework for Climate Services.

Research priorities:

  • Evaluate potential predictability of sub-seasonal events, including identifying windows of opportunity for increased forecast skill
  • Understand systematic errors and biases in the sub-seasonal to seasonal forecast range
  • Compare, verify and test multi-model combinations from these forecasts and quantify their uncertainty
  • Focus on some specific extreme event case studies.

The first phase of S2S will be concluded in November 2018. The plan for the 2nd phase of S2S for an additional 5 years has been endorsed by the WWRP Scientific Steering Group and the WCRP Joint Scientific Committee, and approved by the WMO Executive Council in June 2018.

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