Cloudbursts

A cloudburst is a sudden and intense rainfall event that significantly alters weather conditions within a short span. Unlike typical monsoon rains that are steady and widespread, cloudbursts are localized, affecting small areas with a large volume of water.

Definitions and Criteria

• India Meteorological Department (IMD): Defines a cloudburst as rainfall exceeding 100 mm in one hour over an area approximately 20-30 sq. km.
• World Meteorological Organisation (WMO): Describes it as rainfall at a rate of 100 mm per hour or more. Refers to the Swedish term ‘skyfall’ which implies 1 mm per minute, equaling 60 mm per hour for short bursts or 50 mm per hour for extended periods.

Mechanisms Behind Cloudbursts

• Occur when strong updrafts in thunderstorms hold large volumes of water high in the atmosphere.
• When these updrafts collapse, the water is released suddenly, resulting in an intense downpour.
• Orographic lifting: Moist air is forced upward by mountains, causing rapid condensation and heavy rain.

Implications and Impact

• All definitions agree that cloudbursts are intense, short-lived, and can cause severe damage such as flash floods and landslides, especially in mountainous regions.
• The affected area might be larger depending on the water flow direction post the burst.