强台风"珍珠"异常路径的特点、成因及预报

通过对强台风“珍珠”路径4个阶段的特点和影响因素的分析,特别是影响台风移动的诸多因子及其对“珍珠”西行北折异常路径所起的作用分析,发现:大尺度环境场的调整(副高脊线东退南落、越赤道气流的变化、弱冷空气的变化等),使环境场对“珍珠”的引导作用减弱。弱环境流场与“珍珠”的非线性相互作用是“珍珠”西行北折的主要原因。SST的分布也有利于“珍珠”的加强和热力结构的变化,并影响“珍珠”的路径。“珍珠”的水平结构变化,特别是其热力非对称结构的变化,对路径的影响更为明显。各种主、客观预报对“珍珠”的移动路径作出了几乎完美的预报。

Analysis and Prediction on the Abnormal Track of Strong Typhoon CHANCHU

Four stages of the track of strong typhoon CHANCHU and the influencing factors are analyzed in this paper,which focuses on those contributing to the abnormal north turn from a westerly track.A preliminary conclusion can be drawn that the adjustment of the large scale circulations,such as eastward retreat and southward downshift of the subtropical high ridgeline,the alternation of cross-equator flow,and the activity of weak cold air,weakened the steering effect of the environmental flow on CHANCHU.The non-linear interaction between CHANCHU and the weak environmental flow is the major reason why CHANCHU made such a sharp north turn from the former steady westerly track.Sea Surface Temperature(SST) distribution favored the intensification of CHANCHU,alternated its thermal structure,and hence,influenced its track.The horizontal structural changes of CHANCHU,especially the alternation of the asymmetrical thermal structure,have had more impacts on the typhoon track.Nearly perfect forecasts on the track of CHANCHU have been made by different prediction centers in either subjective or objective products.