The equation of kinetic energy is used to calculate the averagekinetic energy budget over the low-latitude area of East Asia duringthe period of time when summer monsoon advanced northward. It isfound that an abrupt change took place in the atmospheric circula-tion over this area during June 17-20, 1979(the onset of the plum rainseason). Meanwhile both the average and turbulent kinetic energies in-creased rapidly and the updraft velocity with the convective precipi-tation intensified over the area. The average kinetic energy originatedmostly from the work done by the pressure gradient force and therapid increase of the average kinetic energy was mostly determinedby the decreased friction term, i.e., by the conversion of the kineticenergy of sub-grid scale to that of grid scale. The development of cu-mulus convection played an important role in the process. The atmos-pheric motion systems of the subtropical westerly jet and easterlyjet on both sides of the South Asia high, the low-level southwestmonsoon over Southeast Asia. the southeast monsoon over the West Pacific and the cross-equator flow near 105°E and 125°E all madesubstantial contributions to the average kinetic energy budget.