What is a cloudburst? How does cloudburst happen?« Back to Questions List


A cloudburst is an unexpected mighty downpour in a short span of time. Normally, cloudburst occurs over a small area in a matter of minutes.  Earlier, cloud was considered as a solid mass of water and the heavy downpour that occurred along with a reverberating sound was believed to have caused by the burst of cloud. Though the concept was proved to be wrong later on, the name continued. 

A rain of over 100 mm( 3.9 inches) in an hour over a limited geographical area is classified as a cloudburst. The rain dumps huge quantity of water causing flash floods and severe damages.  Hail and thunder accompany majority of cloudbursts thereby increasing their severity.  

Cloudburst, rain, skyfall, cause, damage, major ones, disaster, flash flood, warm air, cool air, storm, rainstorm, droplet

Most often cloudbursts are resulted from storms. For the phenomenon to happen presence of both warm air and cool air are required. The air current rushing upwards in a rainstorm contains huge quantity of water. When these saturated clouds are prevented from raining because of the upward movement of warm current air, circumstances suitable for cloudbursts are created.  The rain drops instead of falling down are pushed upwards. The size of existing drops increases and new drops get formed.  When the vertically formed storms mature and when the raindrops become heavier, the speed reduces and sudden condensation occurs. The entire water contained in the rainstorm showers over a small area.

Cloudbursts happen mostly in interior regions of continental landmasses, hilly regions and deserts.  Open sides of mountains are most conducive area for severe cloudbursts. This is because of the presence of vertically upward moving heated air currents.  However, cloudbursts are rare because it needs presence of both warm and cool air as mentioned above.  Further, they get reckoned only when severe damage of life and property are reported. 

A rain is reported as a cloudburst if the rain measured is more than 100mm in an hour. It is not a standard one and the definition varies from country to country. In Sweden, the term that is used to denote such a condition is skyfall.  A short burst of more than 1mm/min and a long burst of more than 50mm/hour are classified as skyfalls based on the definition given by  the Swedish weather service.

In a cloudburst, sometimes rain of more than 20 millimetres fall in a few minutes. The consequences of cloudbursts can be devastating. They result in flash flood creation with resultant loss of life and massive damages to infrastructure, property and cultivation. 

Cloudbursts are reported from various parts of the world. Some of the major disasters are 
A.    57 inches of rain in 10 hours in Mumbai, India on July 25,2006
B.    91.6 inches of rain in 20hours in Ganges Delta of Bangladesh/India on January 8, 1966
C.    54 inches of rain in 24 hours in Uttarakhand, India on July 1, 2016
D.    8.1inches of rain in 20 minutes in Curtea De Arges, Romania on July 7,1947
E.    1.5 inches of rain in one minutes in Basse-Terre, Guadeloupe on  November 26,1970
F.    9.84 inches of rain in one hour in Leh, Jammu and Kashmir, India on August 5,2010

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