WHY HAS THE MONSOON COME EARLY THIS YEAR?

THE CONTEXT: The southwest monsoon, delivering over 70% of India’s annual rainfall, is a lifeline for its agrarian economy, hydropower generation, and water security. The IMD announced the monsoon’s onset over Kerala on May 24, 2025, eight days ahead of the climatological mean of June 1, marking the earliest onset since May 23, 2009, and one of only five such early onsets since 1950.

• • The early arrival sparked discussions on its causes, implications, and whether it signals a robust monsoon season. Historical data indicates that while early onsets are celebratory, they do not always correlate with bountiful rainfall, as seen in the 2009 drought despite an early onset.

WHAT IS THE SOUTHWEST MONSOON?

The monsoon is a seasonal wind system driven by the differential heating of land and sea. In summer, the Indian landmass heats up faster than the surrounding oceans, creating a low-pressure area that draws moist winds from the Indian Ocean. These winds, laden with water vapor, bring heavy rainfall. The monsoon arrives in two branches: the Arabian Sea branch, hitting Kerala first, and the Bay of Bengal branch, affecting northeast India.

• • Inter-Tropical Convergence Zone (ITCZ): A belt near the equator where winds from the northern and southern hemispheres meet, forming clouds and rain.  It is a global rain-making zone that shifts north in summer, triggering the monsoon.
  • Monsoon Trough: A low-pressure zone stretching from northwest India to the Bay of Bengal, acting like a highway for rain clouds.
  • Somali Jet: Strong winds blowing across the Arabian Sea, carrying moisture to India, like a conveyor belt for water vapor.
  • Madden-Julian Oscillation (MJO): A 30–60-day cycle of clouds and winds moving eastward across the Indian Ocean, boosting rainfall when active, like a traveling rain enhancer.
  • Mascarene High: A high-pressure area in the southern Indian Ocean that pushes moist winds toward India, acting like a pump.
  • Heat-Low: A low-pressure area over northwest India due to intense summer heat, pulling in moist winds like a vacuum.
  • El Niño and La Niña: Climate patterns in the Pacific Ocean. El Niño (warmer waters) often weakens the monsoon, while La Niña (cooler waters) can strengthen it, like distant weather influencers.
  • Indian Ocean Dipole (IOD): Temperature differences in the Indian Ocean. A positive IOD (warmer western waters) boosts monsoon rainfall, while a negative IOD may reduce it, like a regional thermostat.

WHY DID THE MONSOON ARRIVE EARLY IN 2025?

The early onset in 2025 resulted from a confluence of atmospheric, oceanic, and local factors aligning earlier than usual. Key drivers include:

• • Madden-Julian Oscillation (MJO): The MJO’s active phase arrived over the eastern Indian Ocean by May 12, two weeks early, enhancing cloud formation and low-pressure systems.
  • Mascarene High: This high-pressure system intensified to 1027 hPa by mid-May, strengthening cross-equatorial winds that feed the monsoon.
  • Somali Low-Level Jet (SLLJ): Winds reached speeds of over 35 knots by May 20, transporting moisture to the Arabian Sea earlier than the usual June peak.
  • Heat-Low over Pakistan-Rajasthan: Established by May 15 with a core pressure below 996 hPa, it deepened the pressure gradient, pulling moist air inland.
  • Sea-Surface Temperature (SST): Arabian Sea temperatures were 0.5–0.7°C above normal, favoring vigorous convection and rainfall.
  • Monsoon Onset Vortex: A cyclonic formation in the Arabian Sea enhanced moisture convergence, acting as a catalyst for early rains.
  • Neutral ENSO and IOD: The absence of a strong El Niño and a neutral IOD created favorable conditions, unlike El Niño years that often delay onset.

IS CLIMATE CHANGE NUDGING THE ONSET CLOCK?

IMD’s 51-year dataset shows a statistically significant (p < 0.1) drift of about 1.1 days / decade towards a later onset since the mid-1970s, yet with sporadic “early-burst” years such as 1990, 2004, 2009 and now 2025. Researchers link the drift to:

• • Indian Ocean warming “hot-spot” that slows cross-equatorial pressure build-up.
  • Arctic amplification altering jet-stream positions, which in turn modulate MJO propagation.
  • Decadal ENSO flavour shifts (more Central-Pacific El Niño events).

The superimposition of anthropogenic warming on natural multi-decadal oscillations complicates deterministic predictions. “Signal meets noise” is now the new normal for monsoon science.

GLOBAL EXAMPLES:

• • The Australian monsoon, influenced by similar ITCZ shifts, also shows increased variability due to climate change.
  • The West African monsoon has seen altered rainfall patterns linked to Atlantic Ocean warming, mirroring India’s challenges.

Sectoral Implications

EXISTING POLICY ARCHITECTURE

• • National Monsoon Mission (Phase-III, 2023-28): Targets a 10 % skill-score gain in > 10-day deterministic forecasts through higher-resolution Coupled Forecasting System.
  • IMD Doppler Radar Network: 43 radars operational; plan to reach 75 by 2027 to close Himalayan gaps.
  • Agromet Advisory ‘Meghdoot’ App: District-wise 5-day crop advisories; adoption < 50 % in half the states.
  • Flash-Flood Guidance System (FFGS): Real-time flood alerts across 30 river basins.
  • Dam Safety Act 2021: Mandates Emergency Action Plans; 70 large reservoirs still non-compliant (CWC audit 2024).
  • NDMA Urban Flood Guidelines 2010: Remain “advisory”, not enforceable; municipal uptake patchy.

THE GAPS AND CHALLENGES:

• • Predictability Plateau in Monsoon Forecasting: Despite advancements in monsoon forecasting, the India Meteorological Department’s (IMD) ensemble-mean onset prediction error remains at ±3 days, and sub-seasonal forecasting, particularly for Madden-Julian Oscillation (MJO) breaks, loses accuracy beyond 15 days. This limits proactive agricultural and disaster planning.
  • Observation Void in Oceanic and Atmospheric Data: Sparse observational infrastructure, including vandalized buoys in the Arabian Sea and limited Argo float coverage in the Bay of Bengal, hampers real-time data collection. Radar-satellite data fusion remains nascent, reducing cyclone and rainfall prediction accuracy.
  • Hydromet-to-Policy Translation Gaps: Only 14 states integrate IMD’s Extended-Range Outlooks into agricultural planning, such as seed and fertilizer logistics, leading to misaligned sowing and supply chain disruptions.
  • Urban Flood Governance Deficiencies: Outdated drainage master plans and encroached floodplains amplify urban flooding, with cities like Bengaluru and Mumbai facing recurrent waterlogging.
  • Socio-Economic and Climate Change Vulnerabilities: Marginal farmers, urban slum dwellers, and northeastern states face disproportionate monsoon impacts due to erratic rainfall, climate change, and inadequate adaptation measures.

THE WAY FORWARD:

• • Seamless Triple-Deck Forecasts: Upgrade IMD’s public portal to deliver probabilistic onset, break, and withdrawal maps at 20-, 10- and 5-day lead times. Legally notify IMD as the single source under the Disaster Management Act, ensuring uniform messaging across ministries. Integrate the feed into the Kisan Sarathi and ONDC (Open Network for Digital Commerce) agri-apps to trigger automated seed, fertiliser and credit logistics.
  • Dynamic Reservoir Rule-Curves: Adopt ensemble-inflow-based rule-curves in pilot basins (Sharavathi, Bhakra) using Supervisory Control and Data Acquisition (SCADA) linked to the Flash-Flood Guidance System. Mandate quarterly audits by the Dam Safety Authority, leveraging the Dam Safety Act, 2021, to enforce compliance. It will simultaneously reduction of peak flood by ≥ 15 percent and hydropower gain of ~6 terawatt-hours nationally.
  • Monsoon Resilience Cells in Hydro-Metros: Constitute city-level Cells that fuse real-time radar, Internet of Things (IoT) rain-gauges and drainage telemetry to run dynamic pump-out protocols. Model municipal by-laws to be issued by the Ministry of Housing and Urban Affairs, backed by Fifteenth Finance Commission performance grants.
  • Block-Level Climate-Smart Agriculture Grid: Deploy IoT soil-moisture probes and micro-Automatic Weather Stations every 10 kilometres, starting with the Krishna and Godavari districts. Feed the data into Kisan vernacular chat-bots that push dynamic sowing and irrigation advisories.
  • Citizen-Science Rain-Gauge Programme: Subsidise open-hardware tipping-bucket gauges via Corporate Social Responsibility funds and Atal Tinkering Labs tool-kits for schools. Auto-ingest crowdsourced data into IMD Web-Map Service after basic quality checks, doubling station density below 500-metre elevation.
  • Open-Access Hydro-Met Data Marketplace: Release raw radar and buoy data after a three-hour embargo under a revised NDSAP schedule; tag them with machine-readable Creative Commons licences. Anchor a sandbox at the National Data and Analytics Platform to nurture start-ups in weather-risk analytics, crop-traceability and catastrophe-bond pricing.

THE CONCLUSION:

An early monsoon is neither boon nor bane per se; it is a stress-test of India’s ability to convert hydrometeorological intelligence into anticipatory governance. The strategic goal is to shift the national conversation from “When will it start?” to “How do we prosper—whatever it does?”

UPSC PAST YEAR QUESTION:

Q. How far do you agree that the behavior of the Indian monsoon has been changing due to humanizing landscapes? Discuss. 2015

MAINS PRACTICE QUESTION:

Q. Discuss the factors contributing to the early onset of the southwest monsoon in India in 2025. Suggest a comprehensive strategy for the government to leverage the benefits of early monsoon while mitigating associated risks.

SOURCE:

https://www.thehindu.com/sci-tech/energy-and-environment/why-has-the-monsoon-come-early-this-year-explained/article69625001.ece