City gets 400mm rain over 57 hours; July total goes beyond 1,170 mm

Continuous showers between Tuesday and Thursday took the city’s rain tally beyond 1,170mm for July. Mumbai recorded 417mm over 57 hours between Tuesday (8.30am)

Continuous showers between Tuesday and Thursday took the city’s rain tally beyond 1,170mm for July. Mumbai recorded 417mm over 57 hours between Tuesday (8.30am) and Thursday (5.30pm), figures revealed, including its second-highest 24-hour rainfall this season and third-highest since 2015.

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The weather bureau downgraded its orange alert to yellow with the possibility of heavy rain between Thursday night and Friday morning, but predicted a reduction in intensity throughout Friday.

Intermittent intense rain spells between Wednesday and Thursday led to waterlogging, traffic congestion, and damage to residential structures.

The Santacruz weather observatory, representative of the suburbs and Mumbai, recorded 191.2 mm rain between 8.30am Wednesday and 8.30am Thursday (second-highest this season). Of this, 110 mm was recorded between 8.30pm Wednesday and 8.30am Thursday. Through the day on Thursday, between 8.30am and 8.30 pm, the weather station recorded 149.2 mm rain.

This took Mumbai’s rain tally for the month to 1,172.6 mm in 16 days, which is 139% of the months’ average rain (840.7 mm). With 1,567.8 mm rain recorded through the season (June 1 to July 16), Mumbai has received 69.3% of its seasonal average rainfall (2,260.4 mm).

“As predicted, rain data showed scattered heavy to very heavy rainfall with isolated extremely heavy falls over 24 hours in Mumbai,” said Mrutyunjay Mohapatra, director-general, India Meteorological Department (IMD). “The break in rain activity on Wednesday afternoon owing to change in wind pattern allowed conditions to enhance for intense rain spells late Wednesday night followed by continuous downpour till Thursday early morning.”

The Colaba weather observatory, representative of south Mumbai, recorded 156.4 mm rain between 8.30am Wednesday and 8.30am Thursday. Of this, 116.6 mm was recorded overnight. However, a sharp dip in rainfall was witnessed on Thursday in contrast to the suburbs with 23.6 mm rain between 8.30am and 8.30pm.

Over the past 24 hours, location-wise highest rain was recorded at Bandra-Kurla Complex (BKC) with 317.4mm, followed by Dharavi and Bandra at 210 and 209 mm respectively. Worli recorded 198.4 mm. IMD classifies very heavy rain as 115.6-204.4 mm, and extremely heavy rain as over 204.5 mm.

“Variations in the distribution of rain within the city are common. Scattered movement of clouds from south of Mumbai along the coast gained more moisture as it moved northwards, enhancing rain activity over the suburbs,” said KS Hosalikar, deputy director general, western region, IMD.

Thursday’s rainfall in Mumbai exhibited an unusual north to south gradient, said Akshay Deoras, PhD researcher at the University of Reading, United Kingdom. “A large difference between rainfall measured at south Mumbai and suburbs on Thursday was unusual considering the relatively uncommon movement of clouds from Colaba towards suburbs. Local factors such as lakes and terrain seem to have abruptly intensified rainfall over suburbs,” he said.

Low-hanging clouds over south and central Mumbai were witnessed covering top floors of skyscrapers on Thursday afternoon. “This is a common monsoon phenomenon where constant influx of moisture from the Arabian Sea leads to the formation of nimbostratus clouds,” said professor Sridhar Balasubramanian, department of mechanical engineering and IDP Climate Studies, Indian Institute of Technology, Bombay.

Meanwhile, owing to less rain in catchment areas that provide water supply to Mumbai, located in Thane and Nashik districts, the city’s water stock stood at 25.8% so far, against 48.8% recorded during this period last year. “Westerly winds are mainly straddling along the coast owing to the moderate strength of offshore trough (weather system). They are not penetrating towards interiors for heavy rain over catchment. The Bay of Bengal needs to produce a system to pull these winds over these areas to recharge the catchments,” said Balasubramanian.

Both meteorologists said usual intermittent light to moderate showers are expected during the weekend and early next week with rain bands expected to move northwards towards Palghar, Dahanu, and south Gujarat.