Abstract: In this paper, making use of observational data, the problem of numerical prediction for subsynoptic disturbance in summer is studied. By using the finemesh prediction model of five level primitive equations the formation of subsynoptic cyclone which cause the heavy precipitation and the intensificationo of low level jet stream have been predicted successfully. After the comparison of the different results of dry and moist model, the important effect of vapor in producing and developing of these circulation systerns is proved. The preliminary result indicates this disturbance is drived mainly by moist convection. In addition, the influence of initial vapor field on the prediction of precipitation and surface situation is also discussed. It is shown that an accurate description of vapor f field is necessary. An experiment shows that the prediction results of precipitation will be improved if corrections and modifications of the initial vapor field are made by using the satellite cloud photograph.