City got 45% excess rainfall in July, next active spell around August 5

A monsoon trough in the vicinity of coastal Maharashtra is also expected to shift southward of its normal position around August 5, which will lead another active rain spell in and around Mumbai, according to IMD

Mumbai: Despite the prolonged, ongoing spell of dry weather in the city, Mumbai this month received 45% excess rainfall. Since July 1, the India Meteorological Department’s (IMD) weather station in Santacruz, taken as representative of the city and suburbs, has received 1244.6mm of rain, as against the normal of 855.7mm. In July 2021, the city had recorded 1122.6mm of rain. The IMD’s coastal weather station in Colaba, meanwhile, received less rainfall in July, recording 852.3mm of rain, which is 16% in excess of the normal 734.1mm for the month.

Mumbai, India - July 23, 2022: Three women share one umbrella while crossing the road in the rain at Prabhadevi, in Mumbai, India, on Saturday, July 23, 2022. (Photo by Satish Bate/ Hindustan Times) (Satish Bate/HT PHOTO)

Past month’s rainfall has also been marked by significant intraseasonal variability. Mumbai received the majority of its July rainfall in just 12 days, as opposed to continuous precipitation spread throughout the month. There was one heavy spell of rain between July 1 and July 3, followed by another wet spell between July 5 and July 8, and then finally a less intense spell between July 12 and July 16. Since July 17, the city has not received more than 43mm of rain in a single day.

Seasonally speaking, Mumbai has so far received 1536.4mm of rain since June 1, including pre-monsoon showers prior to the official onset of the monsoon over the city on July 11. This is 143.6mm more than normal for the season, up to July 31. Official forecasts presently do not indicate any revival of the monsoon before August 5.

“The dry spell in Mumbai since July 16 can be explained by the lack of any low-pressure systems in the Bay of Bengal, which help to draw moisture over the west coast. However, a low-pressure area is expected to form again around August 5, which can bring heavy rains to the city again,” said Akshay Deoras, a meteorologist and researcher at the University of Reading, UK, who closely tracks the southwest monsoon over India.

A pulse of the Madden-Julian Oscillation, an eastward moving disturbance of clouds, is expected to move into the Indian Ocean over the next two weeks, leading to a spurt in convective activity that is necessary for forming rain-bearing clouds. A monsoon trough in the vicinity of coastal Maharashtra is also expected to shift southward of its normal position around August 5, which will lead another active rain spell in and around Mumbai, according to an official with the IMD’s regional forecasting centre in Mumbai.