A one-way coupled hydrologic and atmospheric modeling system (CHAMS) is developed, which consist of the mesoscale atmospheric model MC2, the Chinese Xinanjiang hydrological model for runoff generation, a flow routing model, and a module for acquiring real-time gauge precipitation. The CHAMS has been used to generate daily precipitation and flood forecasts in real-time for the flooding seasons of 2005 ～ 2009 over the Wangjiaba (30,500 km~2), parts of the HRB. The ultimate goal of this study is to extend the lead time of real-time flood forecasts beyond 5 days. We run MC2 daily to produce a 96-h precipitation forecast, and then use the combined gauge-model precipitation to drive the hydrological model off-line to forecast the hydrographs at Wangjiaba that is the outlet of Wangjiaba sub-basin. We examined the daily forecasts for the 10 major flood events encountered in the past five flooding seasons. The 38 daily hydrograph forecasts from the 10 events with different lead times compare reasonably well with observations. The flood peak of the 10 events is predicted well in both timing and intensity. The peak discharge and the peak time forecast success rates respectively are 81.6% and 78.9%, although the skill of our daily hydrograph forecasts is not uniform over different forecast days. The results demonstrate a good performance of an extension of flood forecasting lead time up to 5 days by coupled hydrologic model and atmospheric models.
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