Cloudburst

Subject: Geography

Section: Natural Disasters

Context: At least 8 dead in cloudburst at Amarnath Cave in Kashmir.

Concept:

The cloudburst is a localised weather phenomena representing highly concentrated rainfall over a small area lasting for few hours. This leads to flash floods/ landslides, house collapse, dislocation of traffic and human casualties on large scale.
Meteorologists say the rain from a cloudburst is usually of the shower type with a fall rate equal to or greater than 100 mm (4.94 inches) per hour or with size droplets 4-6 millimetres at a speed of 10 metres per second.
The primary reason behind this is rising temperatures which, in turn, have led to an increase in precipitation across the Himalayas.

How does it form?

Generally, cloudbursts are associated with thunderstorms. The air currents rushing upwards in a rainstorm hold up a large amount of water.
If these currents suddenly cease, the entire amount of water descends on to a small area with catastrophic force all of a sudden and causes mass destruction.
This is due to a rapid condensation of the clouds.

Prone areas

They occur most often in desert and mountainous regions, and in interior regions of continental landmasses.
The topographical conditions like steep hills favour the formation of these clouds in the mountainous regions. And also, the devastations, as water flowing down the steep slopes bring debris, boulders and uprooted trees with great velocity damaging any structure that comes in their way.
The Chhota Nagpur plateau spread across north Odisha, West Bengal and Jharkhand is the world’s most vulnerable spot for formation of severest thunderstorms.
Cloudburst can occur not only in the monsoon seasons but also during March to May which is known for severe convective weather activities.

Prediction

The large-scale features, which are conducive for occurrence of severe thunderstorms associated with cloudburst, are predictable two to three days in advance.
However, the specific location and time of cloud burst can be predicted in NOWCAST mode only, i.e., a few hours in advance, when the genesis of thunderstorm has already commenced.
To detect these sudden developments, a Doppler Weather Radar (DWR), a powerful tool for time and location specific prediction of cloudburst, can be deployed a few hours in advance. Coupled with satellite imagery this can prove to be useful inputs for extrapolation of cloudbursts anywhere in India.