利用NCEP1° ×1 °逐6h再分析资料、常规天气资料、中尺度自动站等资料,采用多种资料综合分析强台风“纳沙”,探讨台风后期南折登陆越南时桂西南局部降水偏少以及“纳沙”残留云系和冷空气共同作用产生暴雨的原因.结果表明,孟加拉湾低压东北移,使中南半岛高压加强,“纳沙”西侧北风加强,导致其偏离原来的路径向偏西南方向移动,对桂西南影响不如预计的大；来自印度洋的水汽输送和来自南海中部偏南气流的水汽输送在海南岛附近汇合北上,使北部湾和广西中部雨量增大；台风东西两侧V分量大小及V分量最大风速轴的走向对台风路径南(北)折有很好的相关性,当V分量最大风速轴左右对称时,台风移向沿原来的方向稳定少变,而当V分量最大风速轴发生偏转时,台风路径可能出现南(北)折,南(北)折的角度大致与V分量最大风速轴与横轴的夹角相当.%Based on NCEP 1° x 1° reanalysis data, conventional observation data and Mesoscale automatic weather station data, the typhoon " NESAT" was comprehensively analyzed. The causes to the less precipitation in southwestern Guangxi due to the south-turn landing of typhoon in Vietnam and the co-influence of "Nesat" residual cloud system and cold air to produce rainstorm were discussed. The results showed that the low pressure of Bengal Bay moving towards northeast strengthened the high pressure of Indo-China Peninsula, the north wind of "Nesat" on its west side strengthened, resulting in "Nesat" moving towards the southwest, the impact on southwest Guangxi was not as large as expected; the water vapor transport from India Ocean and the South China Sea converged in Hainan Island and moved northward, Beibu Gulf and Central Guangxi rainfall increased; V wind at east and west sides of typhoon and the direction of the axis of maximum V wind were in good correlation with typhoon path south-turning( north-turning). When the axis of maximum V wind was symmetrical, typhoons moved along the original way, when the axis of maximum V wind was deflected, typhoons path might appear south-turning (north-turning) , the angle is equivalent to the angle between the axis of maximum V wind and the horizontal axis.
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