Abstract: Observational data of a selected heavy rain by the Mei-yu vortex in the middle and lower reaches of the Yangtze River in July 1991 are put through a self-adaptive treatment by use of the method of Barens' stale separation. A set of equations for niteractions of kinetic energy is then used to describe the sources (sinks) and interactive processes for synoptic and sub-synoptic stale systems at layers of the troposphere within the area of the vortex in both the developing and maturing stages. The results show that the kinetic energy produced by interaction between wind and mass fields of both scales transforms into the synoptic arid mesoscale systems. It is a sing of energetics for a developing system.