中文摘要：

1323号台风菲特突然西折和近海强度维持是业务预报的主要难点,也是其风雨预报偏差的主要来源。本文利用常规气象观测资料、实时业务数值预报模式和NCEP再分析资料（1°×1°）,对＂菲特＂的特点和预报难点以及造成强风雨的成因进行了综合分析。主要结论如下：东亚高空副热带西风急流迅速增强导致副热带高压加强西伸是＂菲特＂路径突然西折的主要原因;副热带西风急流入口区右侧的强辐散是＂菲特＂近海强度维持及其北侧强风雨发生的主要动力机制;＂丹娜丝＂的存在除了为＂菲特＂强降雨的发生和维持提供充足的水汽输送外,还有利于副热带高压的西伸,也是＂菲特＂路径发生西折的主要原因之一;业务预报中,对对流层高层流场（尤其是副热带西风急流）的分析以及双台风相互作用的关注不够,可能是＂菲特＂路径、强度和风雨预报出现较大偏差的重要原因;此外,当台风路径集合预报发散度较大或不同集合预报系统出现截然不同的路径预报结果时,采用多模式集合预报订正技术将是提高台风路径预报准确率的有效途径之一。

英文摘要：

By using the observation data,operational model data and NCEP reanalysis data（1°×1°）,the characteristics and forecasting difficulties of severe Typhoon Fitow（No.1323） and the cause for the strong wind and heavy rainfall are analyzed synthetically.The results show that Fitow moves westward suddenly and intensifies near the offshore,and these are the major forecasting difficuties in operation and reasons of the big forecasting errors.The subtropical jet over East Asia intensifies rapidly and the subtropical high extends westward,causing Fitow to move westward suddenly.The strong divergence in the right side of the subtropical jet’s entrance is an important dynamic mechanism for Fitow to intensify near the offshore and for the heavy rainfall and strong wind in Fitow’s north side.Danas（No.1324） provides plentiful water vapor transport,bringing the heavy rainfall and causing Fitow’s intensity to sustain near offshore.In addition,Danas makes the subtropical high extend westward.Therefore,the existence of Danas is also an important factor causing Fitow to move westward suddenly.When forecasters failed to pay enough attention to the upper-level fields,especically subtropical westerly jet,which is likely the main reason of the bigger forecasting errors of the track,intensity,rainfall and gale of Fitow.Finally,when the tracks of the ensemble prediction systems have large divergence or the different models produce greatly different forecast results,the ammending technique based on multi-model ensembles is an effective method to improve the accuracy of typhoon track forecasting.