Kolkata experienced record-breaking rainfall, exceeding 200 mm in just two days, surpassing the previous 14-year high of 174 mm set in 2007. This deluge has led to widespread flooding in airports, hospitals, and roads, with the meteorological department forecasting continued heavy rainfall for at least another day. The Regional Weather Centre in Kolkata reported 20 centimeters of rain in Alipore, 22 centimeters in North Kolkata, and a staggering 24 centimeters in the Salt Lake area over the past two days. Meteorological officials confirm this as the highest two-day rainfall total in 14 years.
This unusual weather pattern is attributed to two significant developments in the Bay of Bengal and South Bangladesh, both influencing Kolkata’s weather. “Whenever a weather system develops over Bangladesh, there’s a high probability of heavy to very heavy rainfall in Kolkata,” explained Dr. GK Das, Regional Met Director.
The formation of a cyclonic circulation over South Bangladesh was predicted to trigger substantial rainfall in Kolkata. The lack of wind within the system caused the cloud mass to stagnate over the city, converting the cyclonic energy into persistent downpours. Met officials confirmed the stationary clouds lingered throughout the day. Moving systems typically result in shorter periods of rain, but in densely populated areas like Kolkata, these systems tend to move slowly, prolonging the rainfall. The low-pressure area is now shifting southwest of Kolkata, with heavy to very heavy rainfall expected in Midnapore and Jhargram in the coming days. Rain activity in Kolkata is anticipated to decrease as the system moves further away, but some rainfall is still expected.
Another low-pressure area is forming off the coast of Odisha in the west-central Bay of Bengal. This development is expected to generate vortices and impact the East Coast in the following week. Many of these weather systems originate in the South China Sea, a known breeding ground for cyclonic formations. While this developing system is not currently in close proximity, Dr. GK Das warns that once it reaches landmass, it will likely cause intense rain in Myanmar before approaching the Odisha and West Bengal coasts. The low-pressure area is anticipated to arrive around September 15th, with its effects noticeable in the region by September 26th. Further observation is needed to accurately predict the weather impact on West Bengal and Odisha.
The delayed arrival of the monsoon in North India this year has also resulted in a delayed retreat, contributing to the heavy rainfall. The monsoon retreat typically begins in the northwest region but has yet to commence and is expected to start by the end of September. Experts, however, rule out the current Kolkata rains as being directly related to the monsoon retreat, which typically begins in mid-October in this region. The India Meteorological Department (IMD) reported that the country will experience an extended monsoon season due to sustained rainfall activity over North India, with no signs of decline until the end of September. The IMD defines the Southwest Monsoon withdrawal from northwest India as a cessation of rainfall for five consecutive days. The formation of two cyclonic circulations over the Bay of Bengal and their westward movement across central and northwest India indicate that the retreat is not yet imminent.
