Abstract
Recent advances of regional ensemble weather predictions could improve the prediction of torrential rainfall and resulted severe floods with a longer lead time. To realize this goal, we have developed an ensemble flood forecasting system, composed of an ensemble Kalman filter and a regional numerical weather prediction model in atmospheric part, and Rainfall-Runoff-Inundation (RRI) model in hydrological part. We applied this system to the Kinugawa flood event in Sep. 2015 and studied the forecast feasibility. Ensemble flood forecasts with lead time of 21-15 h were successful in quantitative prediction of a flood discharge peak, while forecasts with lead time of 33-27 h showed a possibility of flood occurrence though its probability was low. The flood forecasting system was superior to deterministic forecasts based on the JMA operational MSM in predictability of flow peak. This study revealed the high potential and limits in predicting flood peaks of the ensemble flood forecasting system.
