Synoptic climatology of pre-monsoon frequent lightning events in Bangladesh

In Bangladesh, there were 1073 lightning-related deaths reported only in May from 2010 to 2021. This figure accounts for 34% of the total lightning-related deaths in the country. A strong sea-level pressure ridge from the north-west and a 500 hPa geo-potential height ridge spanning across north-west to south-east Bangladesh favour frequent pre-monsoon lightning. The elongated low-pressure trough over the Gangetic plains of India towards Bangladesh is a very unique geo-characteristic for convective activity in May. Heightened pre-monsoon lightning activity is also due to a very strong temperature anomaly coupled with an associated convective precipitation system that is triggered by topographic forces from the Shillong Plateau and the Chittagong Hill Tracts. The southerly to south-westerly low-level jet assists moisture transport from the Bay of Bengal in the pre-monsoon. Further, the north to north-westerly subtropical jet stream provides conditions that are conducive to the development of frequent pre-monsoon lightning activity. Moreover, convective available potential energy (CAPE) all over the country in May destabilises the country’s atmosphere with numerous thunderstorms. Precise information of the pre-monsoon climatological anomaly and the associated atmospheric stability indices can be beneficial for the management of lightning-related deaths in Bangladesh.