Numerical simulation of a severe late afternoon thunderstorm over Peninsular Malaysia

This paper presents a numerical study of the genesis and development of a tropical afternoon thunderstorm system over the central part of the western coast of Peninsular Malaysia on 10 June 2007. An attempt was made to numerically simulate the occurrence of the westward propagating rain system using the Pennsylvania State University — National Center for Atmospheric Research fifth-generation Mesoscale Model (MM5). The prevailing wind convergence at the lower troposphere increased the humidity and instability of the atmosphere. The results illustrate that convection was initiated due to surface heating and became stronger in the early afternoon. The convective activity was further enhanced by the interaction between the sea breeze from the Straits of Malacca and the strong easterly winds from the South China Sea. Due to orographic settings, the convergence of these wind systems occurred in the vicinity of the Klang Valley area and led to heavy rainfall that caused a flash flood in the affected region. This case study suggests that land and sea breeze circulations, modified by local topography are potentially crucial to the initialization and development of severe afternoon thunderstorms over the western coast of Peninsular Malaysia.