A cloudburst is sudden copious rainfall. It is a sudden aggressive rainstorm falling for a short period of time limited to a small geographical area.
They are called ‘bursts’ probably because it was believed earlier that clouds were solid masses full of water. These violent storms were attributed to their bursting.
There are similar names for such events in other languages. For example, in Polish the equally vague term used is “Oberwanie Chmury”.
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.
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.
They occur most often in desert and mountainous regions, and in interior regions of continental landmasses.
Cloudbursts descend from very high clouds, sometimes with tops above 15 kilometers. 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.
During a cloudburst, more than 2 cm of rain may fall in a few minutes. When there are instances of cloudbursts, the results can be disastrous.
Rapid precipitation from cumulonimbus clouds is possible due to so called Langmuir precipitation process in which large droplets can grow rapidly by coagulating with smaller droplets which fall down slowly.
During a cloudburst, more than 2 cm of rain may fall in a few minutes. They are called ‘bursts’ probably because it was believed earlier that clouds were solid masses full of water. So, these violent storms were attributed to their bursting.
One of the major disasters from a cloudburst in India occurred in 2002 in Uttaranchal. Some 28 people died when villages like Marwari, Kotsisham, Matgoan and Agonda were hit by sudden cloudbursts.
Cloudbursts frequently occur in Himachal Pradesh during the monsoon.
World Record Cloudbursts
1 minute: 1.5 inches (38.10 mm) at Barot, Guadeloupe, 26 November 1970.
5 minutes: 2.43 inches (61.72 mm) at Port Bells, Panama, 29 November 1911.
15 minutes: 7.8 inches (198.12 mm) at Plumb Point, Jamaica, 12 May 1916.
20 minutes: 8.1 inches (205.74 mm) at Curtea-de-Arges, Romania, 7 July 1947.
40 minutes: 9.25 inches (234.95 mm) at Guinea, Virginia, USA, 24 August 1906.
On August 14, 2007, at least 100 people were feared washed away in flash floods caused by cloudburst at a village near Shimla, India.
In July 2007, close to 30,000 people were displaced in Kerala after a cloudburst & flash floods following it