| The rainstorm event in 15 Apr i I 2002 in South Shandong was a typical meso-scale weather process, but it was misforecasted by weather numerical-model (T213) and operational weather service. In this paper, firstly large-scale air circulation and weather system evolution are analyzed , and get the scale feature and spread process of the meso-scale convective system by analyzing time-space layout of precipitation and satellite cloud maps. The Lower resolution of T213 model and less time-space resolution of data were responsible for the above mentioned misforecast. In this study , the event is simulated by MM5v3.6 with two-way-interaction and triple nested grid. The simulation results reveal that water vapor transportation northward is responsible for the generation of the convective instability in South Shandong, and the easterly wind from sea, gravity wave and convergence generated by southward invasion of weak cold air in PBL play main role in trigger, transmission and enhancement of convective systems. The dynamical structure of the convective system at cl imax is studied and the air flow field is dep i cted. The ana I yses further show that north J i angsu and north Annul is water vapor source of the rainstorm, and the inclining flow of wet air mass in PBL is the main water pass of convective systems.
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