Ensemble forecasting techniques have made significant progress in recent years and proved to be essential in hydrological forecasts. There is an ever increasing expectation for good forecast quality as many more organisations, including basin authorities, water managers and emergency response authorities, adopt ensemble forecast systems. The value of ensemble forecasting is even more apparent considering its potential socio-economic benefit for public safety and reservoir management.

However, more research is still required to improve not only the reliability of meteorological forecasts, through post-processing and downscaling techniques, but also to assess all the predictive uncertainties involved in the hydro-meteorological forecast chain. Forecast predictability can be further enhanced through data assimilation and new strategies for communicating uncertain forecasts can contribute to provide useful information to decision-makers.

The session aims to bring together scientists from meteorology, hydrology and social sciences, as well as practitioners and stakeholders to evaluate the potential of ensemble forecast techniques in pre-operational and/or operational forecasting systems. Contributions will cover but are not restricted to the following topics:

- Hydro-meteorological ensemble forecasting studies with different hydrological and climatic regimes that can lead to a reliable assessment of the ensemble techniques;
- Methods or standards that have been developed to assess or benchmark the performance of ensemble rainfall-runoff modelling;
- Pre- and post-processing of forecasts;
- Methods and products for efficient communication of probabilistic forecasts and their use in practical decision making;
- Practical applications of ensembles in operational systems.

We encourage contributions that also document problems and failures encountered in the practice of operational ensemble forecasting.

Solicited speakers:
John Schaake, John.Schaake@noaa.gov
Massimiliano Zappa, Massimiliano.Zappa@wsl.ch