What is a cloudburst?
The only difference between a cloudburst and rainfall is the amount of water pouring down on the surface of the earth. Cloudburst typically means a huge amount of rain water (typically 100mm over an hour) suddenly falling down on a very small area. There are different definitions of what constitutes a cloudburst in different countries. Sweden for e.g. believes that anything above 50mm per hour for longer rainfalls is a cloudburst. Nevertheless, these downpours are capable of causing damaging flash floods but luckily, these are not very frequent.
How does cloudburst occur?
When hot, moist air reaches the foothills of a mountain and is carried upward, it results in rapid condensation (cooling down). With more and more condensation, the water droplets coagulate thus becoming too heavy to sustain themselves at that place and falling down suddenly in the form of heavy rain. You can imagine cloudburst as a water balloon which when punctured dumps the entire amount of water it carried. Cloudbursts are also accompanied by thunderstorms. They are infrequent because they occur only due to orographic lift (i.e. when hot air parcel moves from a low terrain to a high terrain, typically in hilly regions, and cools down rapidly).
Examples
While cloudbursts were reported at several places in the past, the June 13 cloudburst in Uttarakhand (India) was one of the most devastating in the recent past. The cloudburst that occurred in the holy places of Rambara and Kedarnath resulted in a downpour of 220mm per hour triggering flash floods. More than 1000 were killed, thousands injured and some thousand more missing till date. The small village of Rambara was entirely swept away and the Indian Army was called for what was one of the most extensive human rescue missions in the history.
There were also other recorded cloudbursts with a downpour of more than a 1000mm in an hour in the past like the one in Foc-Foc, France (1966), Pithoragarh, India (2016) and Ganges Delta, India/Bangladesh (1966).
Human and the Climate 