Observational and numerical analysis of the characteristics of MCS development associated with trigger effect of isolated islands

In order to clarify the characteristics of Mesoscale Convective System (MCS) development and understand the impact of the trigger effect of isolated islands, observational and numerical analysis of the heavy rainfall were carried out over the southwestern part of the Korean Peninsula on July 14, 2004. Satellite based remote sensing data and numerical model MM5 with observational data adjustment were used in this study. The MCS development, in this case, was accompanied not by directional wind shear, but by speed shear which was strongly associated with development of the updraft cloud. An inversion layer at a 750 hPa level is one of the fundamental factors in increasing instability. Effective separation of the upper and lower level atmospheric structure due to an inversion layer at a 750 hPa level creates a suitable condition to develop a MCS. According to numerical analysis it has been found that isolated islands located off the southwestern part of the Korean Peninsula are not a principal factor in causing the heavy rainfall due to the evolution of MCS in this case. Transferable topographic forcing of the downwind side can often induce the variation of MCS intensity, while associated with the precipitation amount over the lee side of the isolated islands at a mature stage of MCS development.