Surface Meso High and Wake Low Associated with Pre-Monsoon Thunderstorm Over the Kharagpur Region

Abstract

Observations recorded under the national coordinated STORM (Severe Thunderstorm Observations and regional Modeling) Programme have been used to study the surface parameters associated with tropical squall line (thunderstorm) with trailing stratiform precipitation. A number of studies indicated the presence of three well known features—a pre-squall meso-low, a squall meso-high and a wake low in the surface pressure field associated with a midlatitude squall with trailing stratiform precipitation. In this paper, an attempt is made to identify these mesoscale features, if any, associated with thunderstorms over Indian region. The study is conducted over Kharagpur region, a part of the Gangetic West Bengal frequently affected by thunderstorms during the pre-monsoon season. The observations from 50 m instrumented micro-meteorological tower and upper air sounding at Kharagpur are used in the study. Doppler Weather Radar (DWR) (at Kolkata) imageries are used to identify the squall line with trailing stratiform precipitation. It is observed that in the squall line with trailing stratiform precipitation shield, the meso-high (MH) is associated with convective line and wake low (WL) exists in the rear of the storm. The position of the meso-high is typically found in the vicinity of the heavy rain directly beneath the downdraft.