For the mitigation of floods and flashfloods, operational nowcast and forecast systems are crucial. This chapter provides practical illustrations of the verification of hydrological ensemble prediction systems with a temporal horizon of up to 5 days.
Section 2 shows the application of two ensemble approaches for discharge nowcasts. The results show that both ensemble approaches have added value compared to deterministic nowcasts.
Section 3 presents the evaluation of an operational flood forecasting system. The system is run with the two deterministic COSMO-2 and COSMO-7 weather forecasts and with the probabilistic COSMO-LEPS weather forecast. The evaluation with several skill scores suggests that decisions that need to be taken with a lead time of 1 day and more should be based on the ensemble forecast.
Ensemble forecasts can be difficult to interpret. Section 4 provides a helpful tool for the estimation of flood peak timing and magnitude based on probabilistic forecasts.