The track,structure and cause of precipitation change of typhoon Muifa are studied with the conventional data,daily NCEP reanalysis data,automatic station data,Doppler radar data,as well as the physical characteristics are also diagnostic analyzed.The results are as follows:when the steering flow in the border of subtropical high is strong,typhoon moves along the steering flow,vice versa; the main reason why Muifa moves westerly is related to the westerly trough.The invasion of cold air at mid and low-level makes the typhoon's warm core destructed and transformed from a barotropical structure to a baroclinic one.The first influence of Muifa is originated from peripheral flow of typhoon,the vapour transportation is weaker,but the duration is long,so the accumulative total rainfall is bigger.The remained cloud system of Muifa,the warm and moist flows from southerly monsoon,peripheral flow of typhoon and the cold air are all responsible for the second stage of rainstorm.In addition,the analysis of radar data and automatic weather station data shows that the mesoscale shear and vortex play a triggering role for the development of convective system.%利用逐日NCEP再分析、常规观测、加密自动站、卫星云图及多普勒雷达等资料,分析了1109号台风“梅花”路径、结构和降水变化的原因,并对“梅花”的物理量特征进行了诊断分析.结果表明:副热带高压外围引导气流较强时,台风沿引导气流方向行进,引导气流较弱时,台风受高空槽的吸引,移动路径产生向西的分量；中低层冷空气的侵入,破坏了台风自上而下的暖心、不对称结构,呈现上暖下冷的稳定结构,趋于向温带气旋变性.“梅花”影响辽宁前期,主要受台风外围气流影响,水汽厚度浅薄,但维持时间长,产生的累计雨量较大.后期台风残余云系,在冷空气的作用下,冷暖空气交界处激发出整层上升运动,同时在台风外围水汽、偏南季风水汽共同作用下水汽厚度增加,更充沛的水汽来源为更强降水提供了有利的水汽条件,在辽宁中南部产生暴雨大暴雨天气.此外,雷达、自动站反映的中尺度切变、涡旋,为对流系统发展起到了触发作用.
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