Workers clear an uprooted tree that fell on a road after rains and strong winds triggered by Cyclone Nisarga, in Mumbai, Wednesday, June 3, 2020
Workers clear an uprooted tree that fell on a road after rains and strong winds triggered by Cyclone Nisarga, in Mumbai, Wednesday, June 3, 2020
Photo: PTI

Mumbai recorded the wettest monsoon this year with the Indian Meteorological Department (IMD) yet to officially declare its withdrawal. The maximum city's Santacruz observatory recorded 3,856 mm of rainfall this season, crossing the all-time high mark.

According to Vagaries of the Weather, a private weather blog, monsoon already withdrew on October 26. However, IMD is yet to declare it officially, though it has hinted that the season is nearing withdrawal.

This creates a record of the most delayed monsoon withdrawal this year. The previous record of the most delayed monsoon withdrawal was in 2010 (October 26).

As per the data shared by Vagaries of the Weather, the Santacruz weather observatory, representative of Mumbai and its suburbs, recorded overall 3,856 mm (151 inches) of rainfall. Similarly, the Colaba weather observatory, representative of south Mumbai, recorded 3,427 mm (135 inches) of rainfall during the same period.

Monsoon spans the months from June to September. However, its withdrawal extended to the second week of October in the last five years.

Over four months, the season saw four extremely heavy rainfall events —one in July, two in August, and one in September, 11 very heavy rainfall events between July and September, and nine heavy rainfall days calculated over 24 hours for Colaba and Santacruz. The heaviest one-day rain spell this season was 332.1mm on August 5 and August 6 at Colaba, followed by 286.4mm rain on September 22 and September 23 at Santacruz. Mumbai also recorded 268.6mm rainfall on August 3 and August 4 and 200.8mm between July 4 and July 5.

IMD data over the past 18 years shows that the highest seasonal rainfall before 2019 was recorded in 2010 —3,327.9 mm over four months (June to September). The annual average rainfall for Mumbai is 2,514mm, while the seasonal average is 2,317mm. The south-west monsoon period for Mumbai is from June to September, with the normal onset date on June 10. However, in 2019, the onset was declared by IMD on June 25.

This year, the onset was declared on June 14, followed by deficient rain of 395mm, making it the lowest June rainfall received in five years. However, Mumbai witnessed above average rainfall (1,502.7mm) in July, the highest since the records began being collated by the weather bureau (1944), followed by highest August rainfall (1,247.6mm) since 1959. Meanwhile, 60 per cent of excess rain was recorded in September at 549.1mm.

Meanwhile, the bulletin by the Regional Meteorological Centre, Mumbai, on Monday afternoon stated, " Though monsoon withdrawal has started from parts of Maharashtra, isolated thunderstorm activity accompanied with rain is likely to occur over the region."

KS Hosalikar, deputy director-general of IMD, (western region) on Monday evening tweeted, "Withdrawal of monsoon starts from North Maharashtra from today onwards. Conditions are favourable for further withdrawal from most parts in the next 24 hours."

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