This is a numerical prediction experiment of a hydrological modeling system - WASH123D. WASH123D is a watershed modeling system simulating water flow and contaminant and sediment transport in watershed systems of 1-D stream-river network, 2-D overland regime, and 3-D subsurface media (Yeh et. al., 1998). The rainfall prediction is provided by a high resolution mesoscale model, Penn State/NCAR MM5. A land-falling hurricane case, Hurricane Floyd (1999), is chosen in this study. A vortex specification initialization scheme (Wang and Frank, 2000) is used in MM5 prediction of Floyd (1999). Recent development of WASH123D is also included.