Mumbai's Monsoon Reversal: July's Record Rains Give Way to August Dry Spell
Mumbai experienced a dramatic swing in monsoon activity this year, with July delivering the fourth-highest rainfall in nearly a decade, only to be followed by an unusually dry August that ranked as the third-lowest in ten years. The India Meteorological Department's Santacruz observatory, considered the city's benchmark, recorded 315.3mm of rainfall between August 1 and 30, according to The Times of India. Only two Augusts in the past decade recorded lower rainfall: 177.2mm in 2023 and 235.2mm in 2018.
The pattern was mirrored in South Mumbai, where the Colaba observatory recorded 164.4mm in August, also the third-lowest in a decade. Colaba had received 111.5mm in August 2023 and 188.7mm in August 2018, as per the same report. The shortfall is notable against the monthly normal of 566.4mm for Santacruz and 482.1mm for Colaba.
The Indian Express reported that the dry spell made August the second-driest in South Mumbai in a decade, with the driest being 2023 (111mm) and 2018 following with 188mm. The report also noted that Mumbai received 2,224mm of rainfall since June, against the seasonal average of 2,390.5mm at Santacruz and 2,102mm at Colaba.
A Stark Contrast with July
The reversal was particularly striking. July had brought abundant rain, with the Colaba observatory recording 1,176.5mm and Santacruz 1,491.9mm in that month alone, according to The Times of India. The Indian Express noted that July received 66 per cent more rainfall than its monthly average.
Unlike the preceding months, when Mumbai experienced several intense spells of rain, August passed without a major heavy-rain episode, resulting in a relatively dry month across the city, as reported by The Times of India.
Experts Point to El Niño and Absent Weather Systems
Meteorologists attribute the deficit to a combination of factors. Mahesh Palawat of Skymet Weather Services told The Indian Express that the absence of weather systems and strengthening El Niño conditions were responsible. "In the month of July, active weather systems were present in the central Bay of Bengal which developed and brought rainfall to the western coast. However, after the first week of August, weather systems developed in North Bay of Bengal, which travelled and brought rain activity to the north-west region, and left the west coast region of Maharashtra, Gujarat amongst others deficient in rain," Palawat said.
The India Meteorological Department (IMD) stated that strong El Niño conditions were prevailing over the equatorial Pacific, with above-normal sea surface temperatures across the central and eastern Pacific, as per The Indian Express. El Niño is known to weaken southwest monsoon winds and lead to below-average rainfall in India.
Weather enthusiast Athreya Shetty, quoted by The Times of India, attributed the subdued August rainfall to the absence of an offshore trough and strong weather systems from the Bay of Bengal. "Frequent incursions of dry air from Central Asia, coupled with strong El Niño conditions and MJO suppression, prevented Bay of Bengal systems from moving closer to the west coast and kept the Arabian Sea largely dormant through the month," Shetty said.
Another weather enthusiast, Abhijit Modak, told The Times of India that the sharp contrast between July and August was largely driven by changing synoptic conditions over the region.
Water Supply Situation Remains Comfortable
Despite the dry August, the city's water supply appears secure. The lakes supplying Mumbai are currently holding around 96% of their total useful water stock, according to The Times of India. The Brihanmumbai Municipal Corporation (BMC) has continued with the existing 10% water cut.
The overall monsoon rainfall remains healthy, with Santacruz close to its seasonal average (2,223.6mm recorded so far, against a normal of 2,318.8mm), while Colaba remains below its benchmark (1,782mm recorded to date, against a normal of 2,094.6mm), as per The Times of India.