This year’s monsoon opened with India’s fifth-driest June on record and rainfall almost 40% below normal levels, followed by a sudden deluge early this month — when about a month’s worth of precipitation was dumped on cities like Mumbai in a single week. Since then, the weather system has stalled into another break, with national rainfall about 24% lower than usual for the time of year as of July 19.
“The number of rainy days and how they are distributed used to be smoother. That’s how farmers developed their crop calendars over the years,” said Raghuram Murtugudde, visiting professor at the Indian Institute of Technology Kanpur and an emeritus professor at the University of Maryland. “Global warming combined with El Niño makes the atmosphere act like a sponge that soaks a lot of water and then pours it all in one place.”
BloombergWith roughly half of the country’s farmland still dependent on rainfall for irrigation, swings between dry spells and violent downpours are disrupting summer crop sowing, jeopardizing rural incomes and raising risks of higher food costs. At the same time, the sudden monsoon pauses are trapping urban corridors in stifling humidity, driving up power demand for cooling.
“India’s monsoon is a long season, so obviously it has a pulsating effect, but this time it’s behaving a bit more aberrantly,” said G.P. Sharma, president of meteorology at private forecaster Skymet Weather Services. “It has become a little mysterious.”
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The erratic shifts are being dictated by steering currents 20,000 feet to 25,000 feet above sea level. Rain-bearing systems are encountering atmospheric blocking patterns at that altitude, causing monsoon depressions to stall or to deflect off course, according to Sharma.“Unlike last monsoon, which largely traveled along its normal path, the current one is not following that track. It is getting blocked,” he said.
The prolonged breaks in typical monsoon rainfall are being exacerbated by the impacts of El Niño, which is forcing air over the subcontinent to sink rather than rise, according to Murtugudde. Even as monsoon winds sweep moisture inland from both the Arabian Sea and the Bay of Bengal, the downward motion acts as an atmospheric lid that prevents rain clouds from forming, turning the ambient humidity into “oppressive heat”, he said.
BloombergBengaluru, in southern India, last week recorded its hottest July day in 112 years, and the India Meteorological Department has warned that daytime temperatures are running about 3C to 5C higher than usual in several regions.
“If you have more breaks, you have more hot periods — that’s what El Niño does,” Murtugudde said. The result is a hyper-reactive weather system that is defying standard long-range forecasting. “Think of India as a popcorn kettle,” he said. “When it gets very warm, kernels will start popping all over the place. It’s very difficult to predict.”
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It’s also unclear whether rainfall will normalize later in the monsoon season. While IMD’s long-range assessment is that total seasonal rainfall will be roughly 94% of the long-term average, private meteorologists say the second half of the monsoon could see wider deficits in precipitation.