Climate forecasts on sub-seasonal to seasonal (S2S) timescales are an emerging and essential part of hydrological forecasting. With horizons ranging from two weeks to a season, these probabilistic forecasts are used in industries such as transport, energy, agriculture, forestry, health, insurance, tourism and infrastructure. This session aims to discuss forecasts of climate variability and extremes on the S2S timescale, in particular:
• Evaluation of forecast skill and quality
• Understand sources of predictability (including weather regime dynamics)
• Understand sources of uncertainty (including ensemble generation and design)
• Discuss and compare seamless forecasting including downscaling and statistical post- and pre-processing
• Present multi-model combinations and grand ensemble forecasts
• Use S2S forecasts for disaster risk reduction activities
• Implement operational climatic forecasting systems
• Create user relevant climate and hydrological information and address the need of stakeholders


The overall aim of the session is to improve understanding on the S2S timescale, and promote its uptake by operational centres and exploitation by the hydrological community. We further aim to capitalize on the expertise of the hydrological research communities to address issues of importance to the Global Framework for Climate Services. We in particular invite presentations from the WWRP/WCRP S2S projects that utilise the newly established S2S project database, and all hydrological relevant applications.