News: IMD clarified that the 2026 Upper Assam floods were caused by prolonged heavy rainfall, not a cloudburst, rejecting media reports.

ABOUT

• IMD Definition: ≥100 mm (10 cm) rainfall in 1 hour over an area of 20–30 sq. km.
• A highly localized and rare extreme rainfall event.
• Often causes flash floods, landslides, and debris flows.
• Some scientists propose a "mini-cloudburst" category for ≥50 mm rainfall in 1 hour.

Cloudburst vs Heavy Rainfall

Cloudburst →

• ≥100 mm rainfall in 1 hour
• Highly localized (20–30 sq. km)
• Causes flash floods
• Rare event

Heavy Rainfall →

• Spread over a larger area and longer duration
• Causes riverine or urban flooding
• Common during the monsoon

Mechanism of Formation

• Intense convective precipitation forms towering cumulonimbus clouds.
• Orographic lifting: Moist monsoon winds rise over mountains.
• Strong updrafts keep water droplets suspended.
• When updrafts weaken, accumulated water is released suddenly as a cloudburst.

Geographical Hotspots

Primary hotspots →

• Uttarakhand
• Himachal Pradesh
• Jammu & Kashmir
• Northeast India
• Western Ghats are also prone due to orographic lifting.
• More common during Southwest Monsoon (July–August).

Forecasting Challenges

• Hyper-localized events (20–30 sq. km).
• Rapid development with very short lead time.
• Doppler Weather Radar blind spots in mountainous terrain.
• Sparse network of Automatic Weather Stations (AWS) and rain gauges.
• High computational requirements for hyperlocal forecasting.
• Conventional observatories often record 3-hour or 24-hour rainfall, making cloudbursts difficult to detect.

India's Initiatives

• Nowcasting: Short-term weather forecasts and alerts for localized extreme weather.

Mission Mausam →

• Doppler Weather Radars increased from 14 (2014) to 50.
• Covers 87% of India.
• 50 additional radars planned.
• Uses Artificial Intelligence (AI) for improved hyperlocal forecasting.

Misuse of the Term "Cloudburst"

• Often incorrectly used for any intense rainfall.
• Can divert attention from governance issues like:
  • Poor drainage
  • Unplanned urbanisation
  • Deforestation
  • Weak early warning systems
  • IMD follows a scientific threshold, while State Disaster Management Authorities (SDMAs) often rely on field observations, leading to inconsistent reporting.

Examples

• 2022 Telangana Floods: Experts attributed flooding to infrastructure issues rather than a cloudburst.
• 2025 Dharali Floods (Uttarakhand): Rainfall below IMD cloudburst threshold; illegal construction and poor drainage were major factors.
• 2026 Upper Assam Floods: Caused by prolonged heavy rainfall, not a cloudburst.