1,502mm rain in Mumbai in July, highest for the month since readings began

The month of July ended with the city recording 1,502.7mm rain, its highest for the month since readings began being collated by the weather bureau (1944). The city

The month of July ended with the city recording 1,502.7mm rain, its highest for the month since readings began being collated by the weather bureau (1944). The city has so far recorded 84% of its average seasonal rainfall. However, deficient rain in catchment areas continued to be a concern. The first week of August, however, could change this as the weather bureau issued an orange alert (heavy to very heavy rain) for Monday and Tuesday and yellow alert (heavy rain) for Sunday. No alert has been issued for Saturday.

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The India Meteorological Department (IMD) said July was also marked by a rare occurrence, the absence of a low pressure (LP) weather systems formed either over the Arabian Sea (AS) or Bay of Bengal (BoB).

The LP system is a region of lower or reduced atmospheric pressure than normal causing weather disturbances including increased precipitation and cloud formation.

“These low pressure systems are crucial for maintaining active monsoon conditions over central India, which witnessed deficit rain in July. The BoB was unusually quiet and thus country-wide rain was below expectation,” said M Rajeevan, secretary, Union earth sciences ministry. “However, Mumbai’s performance was exceptional with the formation of smaller weather systems that ensured good rainfall.”

Mrutyunjay Mohapatra, director-general, IMD, said, “Factors such as offshore trough, embedded vortex (localised circulation) and a mid-tropospheric cyclonic system over Gujarat region during different intervals in July led to this performance.”

Independent meteorologists had a different view. “While no monsoon depression had a genesis over the BoB, AS or adjoining land areas, two LP circulations were observed over BoB and adjoining areas (around July 5 and July 14) and three others over AS (July 2, 9 and 17). The systems had strength equivalent to at least monsoon LP areas,” said Akshay Deoras, independent meteorologist and PhD researcher at the University of Reading, United Kingdom.

Mohapatra added that a latest LP system over BoB was expected to form over the next couple of days leading to heavy to very heavy rain for Mumbai and west coast between August 4 and 6.

“Every monsoon is different. August and September should be good for entire season performance. Excess rain in July for Marathwada and parts of Vidarbha is a good indicator for farmers. The next one week, the west coast is likely to be active,” said KS Hosalikar, deputy director general, western region, IMD.

On Friday, water stock at seven lakes supplying water to Mumbai was 34.4% against 85.6% last year. Professor Sridhar Balasubramanian, department of mechanical engineering and IDP Climate Studies, Indian Institute of Technology (IIT), Bombay said, “Heavy to very heavy rain for the coming week will be good for catchment areas, but will come with inconvenience in form of heavy waterlogging and local flooding.”

In June and July, Mumbai suburbs recorded excess rain (42%), which was the highest for any Konkan district, while south Mumbai recorded 40% excess for the period. However, neighbouring districts Palghar and Thane both recorded 29% and 17% deficient rain.

Maharashtra recorded 5% excess rain with 563.9mm average for June and July, against the normal for the period of 538.5mm. Marathwada recorded 42% excess rain, the highest among the four subdivisions, while central Maharashtra recorded 11% excess rain, but 12% deficiency was recorded for Vidarbha. Overall, India recorded normal rainfall for June and July with 10 states recording deficient rain and Jammu and Kashmir recording large deficiency.