Cloudburst in India: Causes, Forecasting Challenges & Assam Floods

Subject: GS Paper 3: Disaster Management

Context: The India Meteorological Department (IMD) recently clarified that the heavy rainfall in Assam and Nagaland did not qualify as a cloudburst, despite media reports linking it to the Upper Assam floods.

About a Cloudburst

• According to the IMD, a cloudburst is: Extremely intense rainfall of 10 cm (100 mm) or more in one hour, occurring over a localised area of about 20–30 sq. km.
• Impact: The intense rainfall exceeds the infiltration capacity of the ground, triggering flash floods, landslides, and soil erosion.
• Mini-Cloudburst: Some scientists advocate classifying rainfall of 5–10 cm in one hour over 20–30 sq. km as a mini-cloudburst.

UPSC Online Coaching

Mechanism of Cloudburst Formation

• Convection: Warm, moisture-laden air rises rapidly into the atmosphere.
• Orographic Lifting: Mountain ranges force moist monsoon winds to ascend, enhancing cloud formation.
• Cloud Development: Cooling and condensation produce towering cumulonimbus clouds.
• Strong Updrafts: Upward air currents suspend raindrops, allowing them to accumulate.
• Sudden Downpour: When updrafts weaken or can no longer support the water droplets, intense rainfall occurs over a small area.

Reasons for Higher Incidence of Cloudbursts in Mountainous Regions

• Orographic Effect: Mountain slopes intensify the upward movement of moist air.
• Steep Terrain: Rapid runoff increases the risk of flash floods and landslides.
• Favourable Regions: The Himalayas and Western Ghats are particularly prone to cloudbursts.

Cloudbursts in India

• Occurrence: Cloudbursts are rare but highly destructive, occurring mainly in mountainous regions.
• Climate Change: A warmer atmosphere holds more moisture, increasing the likelihood of extreme rainfall events.
• Recorded Incidents: The IMD recorded around 30 cloudbursts between 1970 and 2016, though experts believe the actual number is higher due to under-reporting.

Governance Concerns

• Misclassification: Heavy rainfall is often incorrectly labelled as a cloudburst despite not meeting IMD criteria.
• Accountability: Such misclassification may divert attention from poor land-use planning, deforestation, encroachment, inadequate drainage, and weak disaster preparedness.

Factors Making Cloudbursts Difficult to Forecast

• Localised Nature: They occur over areas smaller than the grid size of most weather models.
• Rapid Formation: They develop within a short duration, leaving little lead time.
• Mountain Terrain: Mountains obstruct radar beams, creating observation blind spots.
• Sparse Monitoring: Limited weather stations and rain gauges reduce real-time detection.
• Computational Constraints: Hyperlocal forecasting requires high-resolution models and significant computing power.

Click to Know UPSC OnlyIAS Coaching Centres

Government Initiatives

• Nowcasting: The IMD is strengthening nowcasting to issue short-term weather alerts for localised extreme rainfall events.
• Mission Mausam: Aims to more than double India’s Doppler Weather Radar network and leverage Artificial Intelligence (AI) for improved hyperlocal weather forecasting.

Check Out UPSC CSE Books

Visit PW Store