Mumbai exceeds average annual rainfall with 50 more monsoon days to go

By, Mumbai
Aug 10, 2020 12:25 AM IST

The city on Sunday surpassed its annual average rainfall of 2,514mm, despite little rain over the weekend. Mumbai received 2,526mm rain from June 1 to August 9, with 50 more days for the season to end on September 30.

HT Image
HT Image

Last year, the city had crossed its annual mean tally on August 25 and received 3,670.2 mm rain over four months. In 2018, Mumbai had not crossed the annual average rainfall mark, with 2,239.6mm rain from June to September. In 2017, the city had recorded 2,946.3mm rain in the entire season.

On Sunday, between 8.30 am and 8.30 pm, no rain was recorded either in the suburbs or south Mumbai. However, the Santacruz weather observatory, representative of the suburbs and Mumbai, recorded 18.4 mm rain over 24 hours (8.30am Saturday to 8.30am Sunday) while Colaba, representative of south Mumbai, recorded 6.2mm of rain.

The weather bureau has issued a yellow alert (heavy rain across isolated areas) for Tuesday, Wednesday and Thursday for Mumbai and Thane. “Weather models have indicated active monsoon conditions over the west coast from August 10-11 onward, with weather factors contributing to enhanced rain activity. Mumbai and surrounding areas are also likely to witness an increase in rain intensity from Tuesday onwards, through the week,” said KS Hosalikar, deputy director-general, western region, India Meteorological Department (IMD).

Independent experts said the city is expected to witness more frequent light to moderate showers in the coming week. “However, there won’t be any severe weather threat until August 14, beyond which there might be some rain enhancement,” said Akshay Deoras, independent meteorologist and PhD researcher at the University of Reading, United Kingdom.

This year, the monsoon onset was declared on June 14. However, it was followed by scattered showers through the month, leading to 395mm of rain for June against its average of 493.1mm, making it the lowest monthly rainfall in five years. However, a contrast in rain activity was witnessed in July, with the month ending with 1,502.7mm rain — it’s highest monthly record since readings began being collated by the weather bureau.

Subsequently, the city and suburbs had both surpassed their seasonal rainfall target on August 5. In the first seven days of August, Mumbai received more rain than it generally receives in the entire month. August rain tally stands at 628.4mm, against mean rainfall of 585.2mm.

IMD classifies 15.6-64.4mm as moderate, 64.5-115.5mm rain as heavy, 115.6-204.4 mm as very heavy, and over 204.5 mm as extremely heavy rain for 24 hours. Through the season, Mumbai (Santacruz observatory) witnessed seven ‘very heavy’ rain days so far (five in July and two in August) with maximum rain recorded between August 3 and 4 at 268.6mm, followed by July 4 and 5 at 200.8mm. Additionally, five ‘heavy’ rain days were recorded, with three in July and two in August.

IMD director-general Mrutyunjay Mohapatra said, “Mumbai’s performance in July was due to factors like the active offshore trough, embedded vortex [localised circulation], and a mid-tropospheric cyclonic system over Gujarat region. However, enhanced rain activity in August was led by the low-pressure system over the Bay of Bengal region and associated weather systems over south Gujarat and the Arabian Sea, which led to intense showers helping the city break rain records.”

Meanwhile, the highest 24-hour rain for weather stations in the Mumbai region was recorded in Colaba between August 5 and 6 at 332mm — the second-highest all-time monsoon rain for the region. This helped south Mumbai cross its annual average rain (2,184.1mm) last week. Rain tally for south Mumbai so far stands at 2,447.2 mm.

Light to moderate rain has been predicted for Monday, and heavy rain across isolated areas is expected from Tuesday onward.


    Badri Chatterjee is an environment correspondent at Hindustan Times, Mumbai. He writes about environment issues - air, water and noise pollution, climate change - weather, wildlife - forests, marine and mangrove conservation

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