In this paper the quasi-geostrophic omega equation involvingcondensational heating is solved to discuss its aplicabilitv to summercyclones over the Changjiang-Huaihe Valley. The contributions of the adiabatic and diabatic processes arealso analysed. The following conclu-sions are thus deduced:(1) The equation can accurately determinethe ascending and descending regions and the locations of their maincentres; (2) The direction of the vertical motion is generally decidedby the adiabatic process while the condensational heating amplifies theupward velocity; (3) Stable precipitation is more important than convection to the formation of the surface depression; (4) Calculation of 500hPa divergence can be used to predict the rain belt, area ofheavy rain and the most possible location of cyclogenesis.