Abstract:Based on the simplified formula of precipitation rate and the divergence equation by the kinematic method, a set of formulas for discriminating intensification, weakening and movement of heavy precipitation area, which is associated with the center of relative divergence of large scale motion, is derived under the condition that theageostrophic departure is greater than the actual winds in both the upper and lower troposphere, i. e., and .By utilizing the derived formulas, nowcasting of heavy precipitation in the Bengby area 0—3 hours in advance has been made and the results are consistent with the observations.It is indicated in the discussion that, under the above-mentioned condition, the ageostrophic motion fluctuates about the equilibrium state of geostrophic vorticity and affects the heavy precipitation area by the variation of the positive center of relative divergence in both the upper and the lower troposphere.