Abstract: The characteristics of mesoscale environment of severe storms over the delta are filtered in scaling to obtain mesoscale disturbances corresponding to effective areas of the storm weather. Analyses show that (1) severe storms usually occur near centers of maxima for non- thermal winds in earlier unstable atmosphere, and (2) during the active phase of severe convection,there is a layer of nondivergence at the lower levels of the PBL and mid-troposphere, respectively. From surface upward, divergent and convergent layers occur alternatively. Over the severe convective areas, there are well-defined centers of mesoscale convergence and divergence.In addition, causes responsible for the formation of convective weather are discussed in this paper preliminarily.