Monday, August 9, 2010

Analyzing Leh's Deadly Cloudburst

A devastating extreme weather event unfolded in the Leh district of Kashmir, India on Friday when a cloudburst produced a deluge of rain causing deadly flash floods and damaging mudslides. The epic event washed away government offices, paramilitary camps and residential homes; and claimed nearly 200 lives, injuring thousands and over 500 are still reported missing.

Leh is known as a 'high altitude desert' region and a heavy downpour is a rare occurrence. In trying to gain a better understanding of the formation of the cloudburst and why it produced such an intense rainfall rate, a physics team from the National Centre for Medium Range Weather Forecasting, near New Delhi, will use an atmospheric supercomputer model to mimic the conditions 24 hours prior to the cloudburst that occurred between 12:30 a.m. – 1:30 a.m. on Friday.

In doing so they will simulate the sequence of events that gave rise to the colossal cloud that collapsed over the typically arid village.
They will feed their supercomputer an enormous amount of data – temperature, wind and humidity, and solar radiation – and allow it to churn the numbers using a set of mathematical equations that dictate how the atmosphere will behave over time.

Weather observations from the past have indicated that cloudbursts usually occur during the monsoon – mainly in August – and over the western Himalayan region. The rain from a cloudburst, which descends from very high clouds, has a fall rate equal to or greater than 3.94 inches per hour. Most cloudbursts come from convective, cumulonimbus clouds that form thunderstorms. The extent of damage that a cloudburst could cause depends heavily on the terrain that is receiving the downpour.

The exact measurement of rain that fell during the cloudburst over Leh is still not available. But it is believed that nearly two inches of rain fell in minutes, continuing for a good thirty.

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