IMD Updated Long Range Forecast for Southwest Monsoon Seasonal Rainfall June–September 2026 and June 2026 Outlook

📌 Summary:

• IMD released second-stage Updated Long Range Forecast for Southwest Monsoon (June–September 2026), revising the seasonal outlook downwards
• Quantitative forecast: All-India monsoon rainfall likely to be 90% of Long Period Average (LPA) ± 4% model error (LPA = 87 cm based on 1971–2020 data) — i.e., on the deficient/below-normal cusp
• Probability distribution: 60% Deficient + 24% Below Normal = 84% probability of below-normal or less rainfall for the country as a whole (vs. ~33% climatological); only 14% Normal and 2% Above Normal probability
• Major shift from April 1st-stage forecast — now signals significantly weaker monsoon than initially anticipated
• Driver — El Niño emerging: Neutral ENSO conditions in equatorial Pacific transitioning towards El Niño; MMCFS and other models indicate El Niño likely to develop during the monsoon season (historically associated with sub-par Indian monsoons)
• Indian Ocean Dipole (IOD): currently neutral, likely to remain neutral (no offsetting positive boost from IOD)
• Regional forecast — Below Normal probability highest in:
  • NW India: 46% (Below) vs 21% (Above)
  • South Peninsula: 45% (Below) vs 21% (Above)
  • Central India: 43% (Below) vs 24% (Above)
  • Monsoon Core Zone (MCZ — rainfed agriculture areas): 43% (Below) vs 24% (Above)
  • Northeast India relatively balanced: 33% (Below) vs 32% (Above)
• June 2026 separately: most likely below normal (<92% of LPA = 165.4 mm) for country as a whole
• IMD uses Multi-Model Ensemble (MME) since 2021, combining MMCFS with global CGCMs
• Implications: agriculture (kharif), water availability, hydropower, drought risk, heat stress, drinking water stress; need for water conservation, contingency planning, drought monitoring, early warning services

🎯 UPSC Relevance: GS1 (Geography — Climatology, Monsoon dynamics), GS3 (Agriculture, Drought management, Disaster preparedness). A below-normal monsoon has cascading effects on rural demand, food inflation, fiscal outlay on subsidies/MSP, and rural employment under MGNREGS.

📝 Prelims Facts:

• LPA for All-India SW Monsoon (June–Sep) = 87 cm (1971–2020 baseline)
• LPA for June rainfall = 165.4 mm
• IMD rainfall categories: Deficient (<90%), Below Normal (90–95%), Normal (96–104%), Above Normal (105–110%), Excess (>110%)
• ENSO = El Niño-Southern Oscillation; El Niño = warm phase, La Niña = cool phase
• IOD = Indian Ocean Dipole; positive IOD usually supports good Indian monsoon
• MMCFS = Monsoon Mission Climate Forecasting System (IMD's coupled model)
• Monsoon Core Zone (MCZ) covers India's rainfed agriculture belt
• 4 homogeneous regions: NW India, Central India, South Peninsula, NE India

🔑 Key Term: Multi-Model Ensemble (MME) — IMD's operational long-range forecast technique (since 2021) that pools simulations from multiple coupled global climate models (CGCMs), including IMD's own MMCFS, to reduce single-model bias.