This paper analyze three process of the first strong rainfall during the flood season in Chuxiong influenced by the Bengal bay storm after the year 2000. It is found that the Bengal bay has a solid low - pressure centre landing at 90°E at 500 to 700hPa, and the southeast of plateau has an east northeast to west southwest shear line connected to the landing low - pressure centre at 700hPa. The subtropical high which control Guangdong Guangxi and Southeastern of Yunnan is stronger and has a larger longitude, and the high pressure from eastern part of plateau to Sichuan trend to strong. The subtropical high has a trend to strong- weaken -maintenance. The upper level trough appears in the eastern part of plateau at 500hPa, and then steered cold air southward movement. The cold air passes through Gansu and central eastern of Sichuan and access to Yunnan province from eastern part of plateau. The moisture flux shows that wind moisture transport belt center in accordance with landing storm center. The storm lands by jumping northward and then move eastwards passing through Yunnan, provides abundant moisture for large - scale strong rainfall in Yunnan.%本文通过对比合成分析2000年以后因盂湾风暴影响造成楚雄州汛期第一场大雨的三次过程，发现此类系统影响时：500—700hPa上孟湾有深厚的低中心在90°E附近登陆，700hPa上高原东南侧有东东北一西西南向切变线与登陆的低中心连接。控制两广和云南东南部的副高较强、经向度较大，高原东部到四川的高压一般偏强，切变南压时，副高一般有强一减弱一维持的趋势。500hPa上高原东部出现高空槽，引导冷空气南下，冷空气路径为从高原东部经甘肃、四川中东部进入我省。水汽通量显示水汽输送带中心和登陆的风暴中心一致，北抬登陆后东移经过云南，为云南大范围强降水提供充足的水汽。
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