Explain the mechanism and occurrence of cloudburst in the context of the Indian subcontinent. Discuss two recent examples.

As per IMD definition, over 100 mm of rainfall in one hour is called a cloudburst. It usually occurs over a small geographical region (20-30 sq.km).

Mechanism of Cloudbursts:

1. In India, cloudbursts often occur during the monsoon season, when the south-westerly monsoon winds bring in copious amounts of moisture inland. The moist air that converges over land gets lifted as they encounter the hills. 
2. The moist air reaches an altitud eand gets saturated, and the water starts condensing out of the air forming clouds. 
3. Such an orographic lifting together with a strong moisture convergence can lead to intense cumulonimbus clouds taking in huge volumes of moisture that is dumped during cloudbursts. 
4. Tall cumulonimbus clouds can develop in about half an hour as the moisture updraft happens rapidly, at a pace of 60 to 120 km/hr.

Occurrence of Cloudbursts:

Cloudbursts, hence, occur mostly over the rugged terrains over the Himalayas, the Western Ghats, and north-eastern hill States of India. The heavy spells of rain on the fragile steep slopes trigger landslides, debris flows, and flash floods causing large-scale destruction and loss of people and property.

IMD is enhancing its automatic weather stations, government will give hourly data that can help map cloudburst-prone regions. Multiple doppler weather radars can monitor moving cloud droplets and help to provide forecast for next three hours.