Subseasonal to Seasonal Prediction

The subseasonal to seasonal timescale provides a unique opportunity to capitalise on the expertise of the weather and climate research communities, and to bring them together to improve predictions on a timescale of particular relevance to the Global Framework for Climate Services (GFCS). A planning group which included representatives from WWRP/THORPEX, WCRP, CBS and CCl drafted the implementation plan, giving high priority to establishing collaboration and coordination between operational centres and the research community involved in subseasonal to seasonal prediction, and to sponsorship of key international research activities. From the end-user perspective, the subseasonal to seasonal time range is a very important one, as many management decisions in agriculture and food security, water, disaster risk reduction and health fall into this range. Improved weather-to-climate forecasts promise to be of significant social and economic value. An integrated decisional framework such as the READY, SET, GO being developed by the Red Cross and IRI, where seasonal forecast provide READY information, subseasonal the SET and weather forecasts the GO stage illustrates the potential benefit of a more seamless approach to predictions. Forecasting for the subseasonal time range has so far received much less attention than medium-range and seasonal prediction as it has long been considered as a `predictability desert`. However, recent research has indicated important potential sources of predictability for this time range which can be realized through better representation of atmospheric phenomena such as the Madden Julian Oscillation (MJO) and improved coupling with, and initialisation 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 forecasts. In particular, the representation of the MJO in models has improved substantially in recent years and some models now have skill beyond 20 days. This has important implications globally due to links between this tropical phenomenon and major modes of variability such as El Nino-Southern Oscillation and the North Atlantic Oscillation. Models are beginning to represent these links and processes better but there is still a need for further improvement. In addition, identifying windows of opportunity with increased forecast skill could be the basis for enhanced, actionable forecasts. However, much more research is needed to explore all the potential sources of predictability and model development is needed to subsequently exploit this potential predictability. The main goal of the proposed WWRP/THORPEX-WCRP joint research project is to improve forecast …