A cloudburst is a sudden, intense, and heavy rainfall occurring over a small geographical area within a very short period, typically producing rainfall exceeding 100 mm (10 cm) per hour. It happens when moisture-laden air rises rapidly, often due to orographic lift when air is forced up by mountains or hills, leading to the formation of cumulonimbus clouds. These clouds accumulate large amounts of water which suddenly falls as heavy rain when the updrafts weaken or cold air pushes down on the clouds. Cloudbursts are often accompanied by thunderstorms and can trigger flash floods and landslides, especially in hilly or mountainous regions. The main reasons cloudbursts happen include:
- Rapid uplift of warm, moist air over mountains causing strong convection currents.
- Formation of large cumulonimbus clouds filled with water droplets.
- Cold air descending on these clouds forcing the sudden release of water.
- High atmospheric moisture and humidity.
- Atmospheric instability with temperature differences at different layers.
- Topographical conditions like steep hills enhancing cloud formation and rainfall.
They are difficult to predict precisely due to their small-scale and sudden nature but are common in regions like the Himalayas during the monsoon season. Climate change is increasing the frequency and intensity of such events by increasing atmospheric moisture capacity.
