Cloudbursts happen when a cloud holds an unusually large amount of moisture and then releases it suddenly over a very small area, usually because rising air currents that were ā€œholding upā€ the rain weaken all at once.

What is a cloudburst?

  • It is an extremely intense, sudden rainfall, typically more than about 100 mm in an hour over an area of roughly 20ā€“30 square kilometres or less.
  • They often lead to flash floods, landslides, and heavy local damage, especially in mountain regions like the Himalayas.

Main causes of a cloudburst

  1. Strong upward air currents (convection)
    • Warm, moist air from lower areas rises very fast and prevents raindrops from falling to the ground.
 * Inside tall cumulonimbus clouds, droplets keep growing larger while being lifted upward, so a huge amount of water gets ā€œstoredā€ in a small region of the atmosphere.
  1. Orographic lifting in mountains
    • When moist air hits a mountain slope, it is forced to climb, cools, and condenses into very dense clouds; this is called orographic lifting.
 * In places like the Himalayan foothills, this lifting builds massive storm clouds that can unload enormous rain once conditions change slightly.
  1. Sudden weakening of the updrafts
    • As soon as the strong upward currents weaken, gravity wins: the builtā€‘up water falls almost all at once, causing an intense downpour over a very small area.
 * This rapid release is what people describe as the ā€œcloud bursting,ā€ even though the cloud does not literally explode; it simply rains out very quickly.
  1. Favourable local weather conditions
    • High humidity, relatively low temperatures at cloud height, and weak horizontal winds help keep the cloud nearly stationary above one spot.
 * Because the cloud does not move much, the rain is concentrated; instead of spreading over a large region, it falls almost entirely on one small valley or town.

Role of climate change and human activity

  • Warmer air can hold more water vapour, so as global temperatures rise, the atmosphere can feed more moisture into storm clouds, increasing the chance of very intense rainfall events like cloudbursts.
  • Studies in India have noted an increase in extreme rainfall events in recent decades, linked to higher greenhouse gas levels and atmospheric pollution.
  • Deforestation, urbanisation, and changes in land use can modify local wind, heat, and moisture patterns, which may intensify runoff impacts (flash floods and landslides) when a cloudburst does occur.

Quick Scoop: key points

  • Cloudburst = sudden, very heavy rain over a tiny area in a short time, often in mountains.
  • Caused by strong updrafts, orographic lifting, high humidity, and a nearā€‘stationary storm cloud that suddenly releases stored water.
  • Climate change and landā€‘use changes do not ā€œcauseā€ a single cloudburst but are making such extreme rain events more likely and more dangerous.

Information gathered from public forums or data available on the internet and portrayed here.