Abstract:Using the Doppler radar data in Changde, Hunan Province and other conventional m eteorological and radar data, the synoptic situation and meso scale system feat ures of a super heavy rain in Hunan province caused by Meiyu front were analyze d. Results show that, the echoes experienced the stages of initial genesis, merg ing, helix band, merging, weakening and decay. The echo cells moved from southw est to northeast all the time, but the full echoes moved from northwest to south east firstly, then moved out from north of Hunan province. The center of echo is low. The train effect is the major character of this event. Even though the inv erse wind regions in the imagery of velocity, the well organized secondary cir culation caused by discontinuous meso scale jet core at the middle level of trop osphere may be the main reason to form and sustain the train effect. The spectra l width is very homogeneous at all levels. This indicates that the stable jet at middle level is the major reason of the long duration of the event.