Cloudburst


A cloudburst is an extreme amount of precipitation in a short period of time, sometimes accompanied by hail and thunder, which is capable of creating flood conditions. Cloudbursts can quickly dump large amounts of water e.g. 25 mm of precipitation corresponds to 25,000 metric tons/km^2. However, cloudbursts are infrequent as they occur only via orographic lift or occasionally when a warm air parcel mixes with cooler air, resulting in sudden condensation. At times, a large amount of runoff from higher elevations is mistakenly conflated with a cloudburst. The term "cloudburst" arose from the notion that clouds were akin to water balloons and could burst, resulting in rapid precipitation. Though this idea has since been disproven, the term remains in use.

Properties

Rainfall rate equal to or greater than per hour is a cloudburst. However, different definitions are used, e.g. the Swedish weather service SMHI defines the corresponding Swedish term "skyfall" as 1 mm/min for short bursts and 50 mm/h for longer rainfalls. The associated convective cloud can extend up to a height of above the ground.
During a cloudburst, more than of rain may fall in a few minutes. The results of cloudbursts can be disastrous. Cloudbursts are also responsible for flash flood creation.
Rapid precipitation from cumulonimbus clouds is possible due to the Langmuir precipitation process in which large droplets can grow rapidly by coagulating with smaller droplets which fall down slowly. It is not essential that cloudbursts occur only when a cloud clashes with a solid body like a mountain. They can also occur when hot water vapor mingles into the cold resulting in sudden condensation.

Record cloudbursts

DurationRainfallLocationDate
1 minuteBasse-Terre, Guadeloupe26 November 1970
5.5 minutesPort Bell, Panama29 November 1911
15 minutesPlumb Point, Jamaica12 May 1916
20 minutesCurtea de Argeș, Romania7 July 1947
40 minutesGuinea, Virginia, United States24 August 1906
1 hourLeh, Ladakh, IndiaAugust 5, 2010
1 hourPune, Maharashtra, IndiaSeptember 29, 2010
1.5 hoursPune, Maharashtra, IndiaOctober 4, 2010
5 hoursLa Plata, Buenos Aires, ArgentinaApril 2, 2013
10 hoursMumbai, Maharashtra, IndiaJuly 26, 2005
24 hoursPithoragarh, Uttarakhand, IndiaJuly 1, 2016
13 hoursFoc-Foc, La RéunionJanuary 8, 1966
20 hoursGanges Delta, Bangladesh/IndiaJanuary 8, 1966
24 hours73.62 inches Cilaos, La RéunionMarch, 1952

Locations

In the Indian subcontinent

In the Indian subcontinent, a cloudburst usually occurs when a monsoon cloud drifts northwards, from the Bay of Bengal or Arabian Sea across the plains, then onto the Himalayas and bursts, bringing rainfall as high as 75 millimetres per hour.

Bangladesh

The uplands adjacent to the Front Range of Colorado and the streams which drain the Front Range are subject to occasional cloudbursts and flash floods. This weather pattern is associated with upslope winds bringing moisture northwestward from the Gulf of Mexico.