Result Showed that the background circulation, which was propitious to activi- ty of meso-scale system in Guangxi province, was composed by the south-deflection position of western pacific subtropical high、the stability of Ural block high and southern asian high.

There had been distinctive climate rule for meso-scale system of heavy-rain because of action of topography.

The results indicated the rainstorm was caused by exciting occurrence and development of mesoscale system under the advantageous general circulation environmental condition.

The result show that mesoscale systems which are blurred in the original streamline fields are clearly discernible in the separated streamline fields.

It is shown that these two events occurred in different synoptic scale environments;the MM5 model reproduces successfully the development of the two weather processes and their relevant mesoscale systems;latent heat release acts a vital role in the development of the weather-side waves process;landuse plays .

The new set of equations is useful in the evaluation of the potential effects of slantwise isentropic surfaces on the evolution of mesoscale systems since the potential temperature θ is included explicitly in the dynamic equations of the new set of equations.