After wettest July ever, August sees 91% rainfall deficit

Mumbai is unlikely to see heavy rain until at least August 15, with the Indian monsoon entering a prolonged break phase. This is due to the El Nino phenomenon and the lack of low-pressure systems and moisture-bearing western disturbances. The city has received just 21mm of rain this month, a 91% deficit compared to historical data. The break monsoon condition is expected to continue beyond August 15. This year, Mumbai received 100% of its monsoon quota of rains in just six weeks, surpassing the seasonal normal by 44%.

Mumbai: Thursday marked 10 days since the city’s last heavy rainfall episode, and if forecasts prove to be right, Mumbai is unlikely to see any vigorous showers before at least August 15, with the Indian monsoon moving into a prolonged break phase across the country. Since August 2, Mumbai has not received more than 10mm of rain on any given day, following what was the city’s wettest July ever on record, which saw 1557.8mm of rain.

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Experts have attributed this to the establishment of the El Nino phenomenon in the equatorial Pacific Ocean, which typically leads to subdued monsoons over India. “This, coupled with the lack of any low-pressure systems in the Bay of Bengal or moisture-bearing western disturbances, have led to the current dry spell,” a scientist with the India Meteorological Department (IMD) said.

According to historical data with IMD, the city’s base weather station in Santacruz typically receives 227mm of rain between August 1 to August 9, whereas this year, it has received just 21mm of rain, a 91% deficit. The IMD’s coastal station in Colaba, meanwhile, has received just 17mm of rain this month, 91% less than the corresponding normal of 189mm. August otherwise accounts for about a third of total monsoon rainfall in Mumbai.

“The break monsoon condition in India is expected to continue until at least August 15. In fact, there is a good possibility of it continuing beyond August 15. The average of the Southern Oscillation Index over the last 30 days is indicating that the ocean-atmosphere coupling of ElNiño is getting established. The coupling was not seen during July 2023, which contributed to good monsoon rain in India,” Akshay Deoras, a research scientist at the National Centre for Atmospheric Science & Department of Meteorology, University of Reading, UK, posted on X.

This year has been an exceptional season as the city received 100% of its monsoon quota of rains in only six weeks. That’s 2,318.9mm between June 25 and August 10. The seasonal normal for the city is 2,318.8mm. As of August 10, the city received 2339.9mm of rain, 44% more than the seasonal normal as of date.