A Numerical Study of the Mesoscale Convective System Observed over Okinawa Island in June 1987

Abstract

A mesoscale convective system (MCS) observed over Okinawa Island in Japan during the Baiu season is studied numerically by using a two-dimensional compressible model with warm-rain cloud physics. The initial formation of the system on the leeside of the mountain and two stages of the evolution (stationary and propagating stages) are simulated. The stationary stage, which is made by the piling of the cold pool in the lower layer for the system to move against the flow as a density current, is more distinguished by the orographic effects of forced lifting to the MCS in the upwind side of the mountain and damming the outflow spreading in the leeside. Once cold-air overflows the mountain crest, the system moves fast upwindward and the propagating stage starts. The simulated MCS has a vertical structure similar to those observed in midlatitude-tropical squall lines.