An objective approach for making heavy rainfall forecasts based on numerical model output and the latest observation

An approach is presented that can make an objective heavy rainfall forecast based on numerical model output and the latest observed rainfall without e mploying historical data. The idea of the approach is that the mean rainfal l intensity R at more than 600 grid points can be obtained from the past 6- h rainfall observations at about 700 stations, the mean vertical velocity o mega(RT) can be derived from R, and then the change of the omega(RT) is cal culated; finally the rainfall forecast can be made by using the changed ome ga(RT), the model-predicted u, upsilon, omega, and specific humidity q. The verification shows that the forecast skill of the approach was better than that of the model during the summer seasons of 1994 and 1995.