Hot, Moist Air From Mediterranean Sparked Freak Storm In India, Meteorologists Say

Meteorologists in India believe a cyclonic circulation over the country's west was what spawned a freak storm that swept over three states on Wednesday, reportedly killing more than 110 people.

And more storms are likely across a wide area of India's north this weekend, according to the India Meteorological Department, or IMD.

The storm flattened homes, felled trees and knocked out power in Uttar Pradesh, Rajasthan and Uttarkhand, pelting the region with sand and rain driven by fierce winds. Many of the victims were killed when homes collapsed.

Squalls and dust storms are common in north India, as the Thar Desert heats up in the weeks before the cooling monsoon rains, which typically begin in the south by early June and work their way up the coast.

"The northern plains have been witnessing temperatures of over 40 degree Celsius [104 Fahrenheit]," Mritunjay Mohaptara, the director general of the IMD, was quoted in The Hindu newspaper as saying.

"There were two sources of moisture — a western disturbance over north Pakistan and adjoining Jammu and Kashmir and easterly winds from the Bay of Bengal," Mohaptara said.

A western disturbance, or WB in meteorological parlance, is an extratropical storm that originates in the Mediterranean and can cause sudden precipitation even in the otherwise dry winter season once over India.

K.G. Ramesh, the director general of the India Meteorological Department (IMD), says Wednesday thunderstorms "coincided with a passing WB which provided moisture and unstable conditions, leading to storms across a wide area."

That combination of factors caused a "cyclonic circulation" over Haryana state, Ramesh say, which ultimately triggered the storm system.

Winds in Delhi, where the storm was less severe than elsewhere, were clocked at just over 40 mph, but meteorologists believe winds reached at least 60 mph, and perhaps as high as 80 mph. A typical thunderstorm at this time of year in northern India would bring top winds closer to 30 mph.

Wednesday's storm brought some rain, but mostly dust. Former Director General of the IMD, Laxman Singh Rathore, tells the Hindu, "In case of a dust storm, due to excessive heating, the water from the clouds evaporates before it could land. So soil is dry and the severe winds lift up this soil up to 500 metres above the land."

Although meteorologists said there were no specific studies on how climate change might affect the formation of such storms in India, "It is generally accepted that the frequency of extreme events will increase as a result of global warming," Ramesh said, according to The Times of India.

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