Basics
- Cloudburst:
- Sudden, extreme rainfall in a localized area (≥100 mm/hr over a few sq. km).
- Common in hilly regions due to orographic lift and moisture-laden winds.
- Mini-cloudburst:
- Smaller in scale, but with intense rainfall (typically 50–100 mm/hr).
- Increasingly reported in recent years.
- Forecasting:
- IMD states that cloudbursts remain “impossible to forecast” due to their highly localized and short-lived nature.
- Mini-cloudbursts, though more frequent, are also hard to predict with current models.
Relevance : GS 3(Disaster Management – Floods , Cloudbursts, Environment – Climate Change)
Recent Rainfall Trends (2025 Monsoon till Aug 31)
- Overall Monsoon (June–Aug 2025): 6% above normal (76.2 cm vs usual 70 cm).
- Regional distribution:
- Northwest India: +26% above normal (Uttarakhand, UP, Punjab, Haryana, J&K, Rajasthan, Delhi).
- Central India: +8.6% above normal.
- Southern Peninsula: +9.3% above normal; August rainfall (25 cm) = 3rd highest since 2001.
- East & Northeast India: –17% deficit despite being the traditional rain-surplus zone.
- September Outlook: Expected above normal rainfall (+9% vs average 16.7 cm), continuing a trend noticed since 1980.
Heavy Rainfall Episodes
- August 2025:
- 700+ instances of heavy rain (≥20 cm/day), 2nd highest since 2021 (behind 800+ in 2024).
- Northern India: August rainfall = 26.5 cm, highest since 2001.
- Drivers of extreme events:
- Interaction between Western Disturbances (from Mediterranean) and Bay of Bengal storms → convergence of moisture → intense rain bursts.
- Resulted in devastating floods and landslides in Himachal Pradesh, J&K, Uttarakhand.
Key Analytical Insights
- Mini-cloudbursts on the rise:
- May be linked to climate change-driven shifts: warming atmosphere holds more moisture, increasing probability of intense short-duration rainfall.
- Urbanization + deforestation in hilly areas amplifies impacts (flash floods, landslides).
- Changing monsoon dynamics:
- September becoming wetter since 1980 (possibly due to delayed monsoon withdrawal + oceanic-atmospheric changes like Indian Ocean Dipole).
- Regional inequality: Surplus in NW & Central India, deficit in East & NE → disrupts agriculture, hydrology, disaster preparedness.
- Forecasting limitations:
- While seasonal/weekly monsoon forecasts improving, sub-hourly localized predictions like cloudbursts remain beyond current radar and model resolution.
- IMD using Doppler radars + AI-based nowcasting to reduce unpredictability.
- Policy & Preparedness Implications:
- Need for micro-level disaster management plans, especially in Himalayan states and urban flood-prone zones.
- Resilient infrastructure + improved early warning systems essential.
