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


  1. The WMO Commission of Atmospheric Sciences (CAS) requested at its 15th session (Nov 2009) that WCRP, WWRP and THORPEX set up an appropriate collaborative structure for subseasonal prediction.
  2. A WCRP/WWRP/THORPEX workshop was held at Exeter in Dec 2010 which recommended formation of a Planning Group to write an implementation plan for an S2S project under WCRP-WWRP-THORPEX sponsorship
  3. The implementation plan was written in 2012, was endorsed by the WWRP and WCRP JSCs, and creation of the Subseasonal to seasonal prediction project was approved by the WMO Executive Council, which also approved the creation of a project office and a trust fund for sub-seasonal to seasonal prediction.
  4. Term of reference were drafted and the first 5-year phase of the project began in Nov 2013.
  5. A report on the first 5 years and a proposal for a Phase II of S2S were published in 2018, including a gap analysis. [S2S Phase II Document]
  6. Phase II of S2S began in January 2019 and will conclude in December 2023.

Research Priorities

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

Scientific issues

  1. Identify sources of predictability at the sub-seasonal to seasonal time-range.
  2. Prediction of the MJO and its impacts in numerical models
  3. Teleconnections - forecasts of opportunity
  4. Monsoon prediction.
  5. Rainfall predictability and extreme events
  6. Polar prediction and sea-ice
  7. Stratospheric processes

Modelling issues

  1. Role of resolution
  2. Role of ocean-atmosphere coupling
  3. Teleconnections - forecasts of opportunity
  4. Systematic errors.
  5. Initialisation strategies for subseasonal prediction
  6. Ensemble generation
  7. Spread/skill relationship
  8. Verification

International Coordination Office

The International Coordination Office (ICO) for the Project Sub-seasonal to Seasonal Prediction Project (S2S) is hosted by the APEC Climate Center (APCC) of the Korea Meteorological Administration (KMA) in Busan, Republic of Korea, since 2021.

The primary function of the S2S-ICO is to provide support to the planning and implementation of S2S priorities, to ensure appropriate international coordination between the S2S participating WMO Members and collaboration with related WMO Programes and other international programes.

  • The S2S ICO supports and coordinates planning and implementation of S2S activities.
  • The S2S ICO provides scientific, technical and secretarial support to the S2S Steering Group.
  • The S2S ICO assists in the cooperation between S2S and other relevant international programs and activities.
  • The S2S ICO assists with organizing appropriate meetings, scientific workshops, training events, conferences and other activities relevant to S2S.
  • The S2S ICO assists with reports, correspondence and publications.
  • The S2S ICO manages the S2S website and project data base.


Postal Address

International Coordination Office for S2S Prediction Project
APEC Climate Center
12, Centum 7-ro, Haeundae-gu, Busan, 48058, Republic of Korea