Expected benefits of ensemble hydro-meteorological predictions comprise higher forecasting skills, improved risk assessment and well-informed decision-making in operational water management. Ensemble hydro-meteorological forecast and warning systems have been developed to improve flood control and drought management, as well as to optimize water allocation and regulation for different uses. Such systems, based on possible future scenarios of meteorological and hydrological variables, are becoming more and more operational and been used in real-time applications across a wide range of sectors and users, including river basin authorities, public agencies, private entities and commercial industries. The change represented by moving from deterministic forecasting systems to a probabilistic framework poses however new challenges for the forecasting community, for the users and the forecasters.

This session will be an opportunity to bring together scientists, forecasters, practitioners and stakeholders interested in exploring the use of ensemble hydro-meteorological forecast techniques in hydrological applications: e.g., flood control, reservoir operation for hydropower and water supply, irrigation scheduling, crop modelling for agricultural management. The session will also explore new forecast products and systems in terms of their implementation and practice for real-time forecasting.

Contributions will cover, but are not restricted to, the following topics:
- The design of ensemble prediction systems
- Requirements and techniques to improve the skill of hydro-meteorological ensemble forecasting systems
- Methods to bias correct and calibrate ensemble forecasts
- Methods to assess the quality or benchmark the performance of ensemble forecasts
- Approaches to deal with forecast scenarios in real-time
- Strategies for balancing human expertise and automation in ensemble forecasting systems
- Challenges of the paradigm shift from deterministic to ensemble forecasts
- Methods and products that include forecaster knowledge to improve the interpretation of ensemble forecasts
- Approaches for efficient training (including role-playing games) on the use and value of ensemble predictions.

The session welcomes new experiments and practical applications showing successful experiences, as well as problems and failures encountered in the use of uncertain forecasts and ensemble hydro-meteorological forecasting systems. Case studies dealing with different users, space-time scales, forecast ranges, hydrological and climatic regimes are welcome.

The session is part of the HEPEX international initiative: www.hepex.org