| Recent advances of regional ensemble weather predictions have increasingly improved predictability of rainfall useful for streamflow forecasts. However, it was not employed yet in Japan. In this study regional ensemble prediction of rainfall by typhoon TALAS (201112) and ROKE (201115) in Kansai area was conducted using an ensemble Kalman filter and regional model, WRF (Weather Research and Forecasting). The predicted rainfall was given to a distributed hydrological model to implement ensemble streamflow forecasts. The ensemble rainfall predictions were not capable to predict point rainfall, but reasonably predicted average rainfall of severe rainfall area in Kii Pen. On the other hand, for Hiyoshi dam catchment, another study area in Hyogo Pref., the results of ensemble predictions were separated; for ROKE case it was quite successful, but for TALAS case it overestimated rainfall significantly. The resulted streamflow forecasts reflected the rainfall predictions. However, the streamflow forecasts utilizing combination of radar observed rainfall and predicted rainfall are quite encouraging for possible use of regional ensemble prediction for streamflow forecasts in Japan. |
