南海台风中期路径趋势判别预报方法

根据历史台风的相似路径将台风分为西行、西北沿海登陆和海上转向三类，并分析了各类500hPa高度场的特征。通过对台风位移与其相应的500hPa高度场的典型相关分析，提取了天气强迫信息，连同台风的一些气候学和持续性特征作为待选因子，采用多级逐步判别方法，建立台风72h路径趋势的各类判别函数。预报时，代入72h500hPa数值预报产品及气候持续性因子。通过对1990～1994年的独立台风进行了试报检验。结果表明，试报的准确率为88.8％，Heidke技巧得分为0．80。该方法为南海台风中期路径趋势预报提供了一种客观方法。

DISCRIMINATE FORECAST APPROACH OF MID-RANGE TRACK TRENDS FOR TYPHOONS OVER THE SOUTH CHINA SEA

Based on the analogy tracks of historical typhoons, the mid - range track trends were classified into three categories: westward travelling, northwestern coast landing and turning over the sea, and respective characteristies of 500 hPa composite height fields were andlyzed. The synoptic forcing information was abstracted using the canonical correlation analysis between the typhoon displacements and corresponding 500 hPa height fields. The synopitic forcing information, together with climatology, persistency characteristics was considered as prediscreening predictors and the multiple stepwise discriminant analysis technique was employed to derive a set of discriminant functions for predicting typhoon track trends at 72h.Both climatology, persistency predictors and the numerical forecast products of 500 hPa geopotential heights from ECMWF were substituted into discriminant functions in predicting motion trends. The independent typhoon cases during 1990 - 1994 were performed as the verifications. The resulting verifications showed that percent correct is about 88. 8% and the Heidke skill score is 0. 80. The approach can be adopted as an objective prediction technique for discriminating mid - range track trends of typhoons over the South China Sea.