0907号热带风暴“天鹅”登陆后异常路径和陆上维持机制的诊断分析

Diagnostic analysis on anomalous track and sustaining over land of the landfall tropical storm 0908 "GONI"

2009年第7号热带风暴"天鹅"在广东省台山沿海登陆,登陆后在粤西上空长时间停留、强度维持,后期路径异常,针对这几方面在预报上的难点进行分析。结果表明:热带气旋在陆上长时间维持与低空水汽通道的连结,高空弱的风场切变有关;热带风暴后期路径第一次西南转向是由于周围环境流场出现变化转向西南的,第二次路径再次产生转向,是受到离它较近的台风"莫拉克"的牵引作用,另外,925 hPa附近θse的高值区或高能轴也可意示"天鹅"的趋向。

Tropical storm 0908＂GONI＂landed on the coast at Taishan city of Guangdong province.After landfall,it rested on the western Guangdong province over air long time and its intensity keeps steady.Moreover,its track in later period was unusual.In view of those aspects,the forecast of tropical storm＂GONI＂is difficult.In this article,the analysis of tropical storm＂GONI＂is carried on.The main conclusions are as follows： tropical cyclone maintenance over land relates to low-altitude water vapor channels＇ linking and high-altitude weak shear of wind field;the tropical storm track turning southwest for the first time is due to the change of surrounding environment flow field;for its second turning,the typhoon＂MORAKOT＂plays the role of traction.In addition,the high value of θse on the levels of 925hPa or the high energy axis could also indicate the trend of＂GONI＂.