City may witness its lowest June rainfall in 5 years

A lull in rain activity over the past 10 days may lead to deficient rain in Mumbai for June with the possibility of the lowest June rainfall in five years.

A lull in rain activity over the past 10 days may lead to deficient rain in Mumbai for June with the possibility of the lowest June rainfall in five years.

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While Mumbai has so far recorded just over 340 mm rain in June 2020, June rainfall was 515.1 mm in 2019, 792.5 mm in 2018, 523.2 mm in 2017, 695.2 mm in 2016, 1106.7 mm in 2015, according to data from the India Meteorological Department (IMD).

During June 2014, Mumbai witnessed its lowest June rain over the past 10 years at 87.3 mm, while the second-lowest was during June 2012 at 298.5 mm. The all-time lowest June rainfall was in 1972 at 0.2 mm followed by 1995 at 82.2 mm.

This year, the Santacruz weather station, representative of the suburbs and Mumbai, has so far recorded 344.4 mm rain between June 1 and June 28 (5.30pm), against the normal rain of 449.6 mm or rainfall deficiency of 23%.

It will take an additional 148.7 mm rain between Monday and Tuesday for the city to meet its monthly target of 493.1mm average June rainfall). However, the weather bureau has predicted only light to moderate showers for both days but an increase in rain intensity is expected between July 3 and 5.

During the same period (June 1 to June 28 5.30pm), Colaba weather observatory, representative of south Mumbai, recorded 389.9 mm rain against the normal rain of 496.5mm, which means rain deficiency of 21.5%.

Monsoon onset this year was declared on June 14, two days later than its new normal onset date of June 11. So far there has been only one intense rain spell on June 18 that led to 41 mm rain in the suburbs and 44 mm in south Mumbai.

However, Maharashtra from June 1 to June 28 received 219.5 mm rain against the normal for the period at 177.1 mm, which is an excess of 24%.

“Significant weather systems did not develop over the west coast of Maharashtra, especially towards Mumbai, that could activate monsoon currents due to the rapid progression of the southwest monsoon over north and northwest India, where onset was declared before the normal arrival dates,” said Mryutunjay Mohapatra, director-general, IMD adding, “However, the performance in July and August is likely to be much better as compared to June as monsoon currents will strengthen over the region.”

Last year, monsoon onset over Mumbai was declared on June 25, most delayed in 44 years. However, the city witnessed its first very heavy rain spell as late as June 28 with 234.8 mm rain over 24 hours helping the city surpass its June average rain.

Independent meteorologists explained that no significant weather systems formed near north Konkan, including Mumbai, resulting in insufficient moisture convergence and weak westerly winds, resulting in below-normal rains so far for June. “It is not due to cyclone Nisarga, since South Konkan has received above-normal rains. This is the inter-annual variability of monsoon, wherein every year it has a different pattern,” said Professor Sridhar Balasubramanian, department of mechanical engineering and IDP Climate Studies, Indian Institute of Technology-Bombay.

Others said south Konkan received more rainfall due to the effect of Cyclone Nisarga and more active monsoon conditions than north Konkan. “The monsoon’s arrival in Mumbai was not that intense, followed by a considerable reduction in the rain due to reduced moisture. Since typical heavy rainfall events were missing for the Mumbai region throughout June, significant rain deficiencies have emerged,” said Akshay Deoras, independent meteorologist and PhD researcher at the University of Reading, United Kingdom.

Both, Balasubramaniam and Deoras concurred with the IMD that as monsoon currents moved north, Mumbai rains went into a break phase. “Even though June is likely to end in deficit rains, the outlook for July looks very good with above-normal rains, which is likely to cover this deficit. “This is due to strong westerlies and a formation of an offshore trough near the west coast,” said Balasubramaniam.

Deoras said, “Rainfall enhancement is possible after July 2. However, there might be subdued rainfall once again from around July 10 due to another possible break-monsoon scenario.”