A Prospect Forecasting Method Study of Severe Convective Weather in Beijing Area

The forming condition and the prospect forecasting method of severe convective weather in Beijing area are studied according to 276 severe weather cases in June, July and August from 1983 to 1992. By means of classification of 500 hPa patterns day by day, the largescale circulation patterns in Beijing area are divided into five types. From the cases of convective occurrence and non-occurrence in each type 298 weather samples are randomly adopted and analysed for studying the circulation pattern and difference of convective occurrence and no-occurrence. It is shown that circulation features, structure and the distribution of the scalars for convective occurrence and no-occurrence are different obviously. Therefore a concept model is summarized and the starting point about circulation pattern forecast is obtained. On this basis, after calculating dozens of physical parameters, the best forecasting factor is selected, and the prospect forecasting technique is developed by use of dicision tree method. The operational experiments in 1993 and 1994 show that the forecasting is objective, fast and automatic.