Cloudbursts have killed over 400 people in South Asia. What are they?

The Indian Meteorology Department defines a cloudburst as heavily localized rainfall of 4 inches in an hour. While forecasters can predict with high accuracy which state or province might see heavy rain, cloudbursts can be difficult to predict due to their local nature, short duration and suddenness — making them the site of heavy destruction and fatalities.

They appear as if the clouds are discharging all their moisture at the same time, like a rain bomb.

“It’s like an overhead tank has burst on top of a house,” said Khalid Khan, a former special secretary for climate change in Pakistan and chairman of the climate initiative PlanetPulse. “The rain that would have taken three days to fall instead falls in one hour.”

The lack of early warning infrastructure in some of the affected areas has added to the fatalities. Buner residents accused Pakistani officials of failing to issue evacuation warnings, saying there were no broadcasts made from mosque loudspeakers, which is a common method in remote areas.

The government said that an early warning system was in place for the district, but the downpour was so sudden that alerts came too late.

There is “no forecasting system anywhere in the world” that can predict the exact location and time of a cloudburst, Asfandyar Khan Khattak, a Pakistani official from Khyber Pakhtunkhwa, told the Associated Press.