Kolkata faced severe traffic disruption on Thursday evening after a powerful thunderstorm brought blinding showers and gusty winds to several parts of the city, even as the southwest monsoon began its seasonal withdrawal from eastern India.
The storm struck on the usual date for the monsoon’s withdrawal from south Bengal. Strong winds sent flowerpots flying from balconies and lightning illuminated the sky, while intense rain slowed or halted traffic in multiple areas. The India Meteorological Department’s Alipore observatory recorded only 2.6mm of rain until 8.30pm, but the figure did not reflect conditions across the wider city, where several locations received significantly heavier showers.
The weather event coincided with the resumption of the monsoon’s retreat after the withdrawal line had stalled over parts of the heartland. The Met office said the monsoon had further withdrawn from the remaining parts of Maharashtra and some areas of Goa, Karnataka, Telangana and Odisha, as well as additional parts of Jharkhand and Chhattisgarh.
The withdrawal of the southwest monsoon generally progresses from west to east, in the opposite direction to its advance at the start of the rainy season. The Met report said conditions were becoming favourable for further withdrawal from parts of eastern India, the northern peninsula and many areas of northeast India over the following three to four days.
Meteorological systems over eastern and central India contributed to the storm. An upper-air cyclonic circulation was located over northeast Bihar and neighbouring areas, while a trough extended from that circulation to Telangana across Jharkhand, Odisha and Chhattisgarh. According to Met officials, these systems were feeding moisture into south Bengal. The moisture, interacting with the prevailing heat, created conditions favourable for thunderstorms.
The episode highlights the uneven nature of rainfall measurement in a dense city. While the official Alipore reading remained low, intense localised showers in other areas were sufficient to affect road movement and create hazardous conditions for pedestrians, motorists and two-wheeler users. The gap between a station reading and neighbourhood-level experience also reflects how short-duration thunderstorms can produce disruption without generating a high citywide rainfall total.
The Met office said the rain was expected to subside from Saturday. It forecast no rain warning for Kolkata and surrounding areas from October 10 to 13. Further monsoon withdrawal from eastern India will continue to be monitored as the weather systems influencing south Bengal weaken or move away.
