Extended Abstract

One advantage of ensemble forecasting is to represent various uncertainties ofweather forecasts. Conventional ensemble products based on model outputswere provided to forecasters. These products included the ensemble mean,ensemble spread, probability of occurrence of some phenomena, stamp chartsTwo selected examples of REPS forecast products for HIW events in monssonseason are presented in some detail. The first example is an squall linehappened in Henan Province (June 3 2009). This squall line process was notpredicted by forecasters, but it was found in retrospect that some REPSs hadpredicted gale. The second case was a successful forecast for the heavyrainfall in Yangtze river on July 9, 2010. From these case, comparing todeterministic forecasts, the advantage of REPS products for predicting thecomplex small-scale summer system over China was very obvious.Fig.5 Stamp chart of 10m wind speed and ensemble mean of modeling radar reflection at500hPa layer for 12h forecasts , which were initialized on 00Z June 3, 20095. Future plansThe Global/Regional Assimilation and Prediction System (GRAPES) has beenrecently developed for the next generation medium-range operational model atChina Meteorological Administration (CMA).CNWP will developedGRAPES-based REPS. The initial perturbation is still a key point of REPS, soCNWP plan to develop initial perturbation such as Singular Vectors, EnsembleTransform Kalman Filter.-295-