Mains Analysis: The northeast monsoon in an El Niño year – why the south must plan for extremes, not averages

26 October 2026 · English Environment & Ecology

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Topics: Environment · GS-I · GS-III · UPSC Mains Analysis

Context

The northeast monsoon set in over Tamil Nadu and the adjoining south peninsula in mid-October 2026. It follows a weak southwest monsoon: the June–September season ended at about 87% of the long-period average (LPA), the largest shortfall since 2015, in a year of a strong El Niño. The India Meteorological Department (IMD) expects below-normal October–December rain for most of India but normal to above-normal rain over the southern peninsula. For Tamil Nadu, which depends on this season for drinking water and the samba crop, the question is not only how much it will rain but how the rain will come – in long dry gaps broken by a few very heavy spells.

Background – how the northeast monsoon works

• Season: October–December; also called the retreating monsoon. As the southwest monsoon withdraws, the winds over the Bay of Bengal turn north-easterly and bring rain to the Coromandel coast.
• Area: IMD's "south peninsula" for this season has five subdivisions – Tamil Nadu–Puducherry–Karaikal, Coastal Andhra Pradesh–Yanam, Rayalaseema, South Interior Karnataka and Kerala–Mahe.
• Importance for Tamil Nadu: the State receives nearly half of its annual rainfall in this season, unlike most of India.
• Rain-bearing systems: low-pressure areas, depressions and cyclones from the Bay of Bengal – October–December is the main post-monsoon cyclone season.
• Variability: the season is far more variable than the southwest monsoon; in El Niño years Tamil Nadu has often received normal or excess rain (the Chennai floods of December 2015 and Cyclone Michaung in December 2023 both came in El Niño years).

Why it matters – key dimensions

Dimension	Issue
Water security	Reservoirs and tanks of Tamil Nadu are recharged mainly in this season; a failure means summer drinking-water stress.
Agriculture	The samba (Cauvery delta) crop and rabi sowing in the south depend on it; a weak southwest monsoon raises the stakes.
Urban flooding	Short, intense spells overwhelm drains in Chennai and other coastal cities built over lakes, marshes and floodplains.
Cyclones	Bay of Bengal cyclones bring wind damage, storm surge and extreme rain in a single day.
Climate change	Fewer rainy days but more very-heavy-rain days make averages less useful; forecasting the extremes matters more.

Challenges

• Forecasting limits: the season is driven by short-lived systems; skill at district level and beyond a few days is still limited.
• Encroached water bodies: loss of tanks, marshes and river margins reduces natural storage and drainage.
• Storage gap: heavy rain runs off to the sea, while the same areas face water scarcity months later.
• Last-mile warning: alerts do not always reach fishers, farmers and slum residents in a form they can act on.

Way forward

1. Move to impact-based forecasting – warnings that say what will happen to a street or a crop, not only how many millimetres will fall.
2. Use the Union government's Mission Mausam (2024) to improve radar coverage and high-resolution forecasts for the south coast.
3. Restore and protect tanks, lakes and marshes; enforce no-construction rules in floodplains; follow NDMA guidelines on urban flooding.
4. Build a "store the surplus" plan – tank desilting, recharge wells and inter-linking of local tanks – so flood water becomes summer water.
5. Strengthen community warning through local bodies, fishers' associations and mobile alerts; plan crop insurance and contingency seeds early.

Mains practice question

Answer framework: Introduction – season, area, share in Tamil Nadu's rainfall · Body – (a) mechanism: retreating winds, Bay of Bengal systems, cyclones; (b) why it is less predictable; (c) impacts: urban floods, agriculture, water security, with one example · Way forward – impact-based forecasting, Mission Mausam, wetland restoration, storage · Conclusion – faculty-view line below.

Prelims pointers

• Northeast monsoon = October–December; retreating monsoon; Coromandel coast gets most rain.
• Long-period average (LPA) is the average rainfall of a long base period; IMD calls 96–104% of LPA "normal" for the southwest monsoon.
• El Niño – warming of the central and eastern equatorial Pacific; usually weakens the southwest monsoon.
• Mission Mausam – approved by the Union Cabinet in September 2024 to make India "weather-ready and climate-smart".
• Sendai Framework for Disaster Risk Reduction 2015–2030; Disaster Management Act, 2005.

Sources: India Meteorological Department – southwest monsoon end-of-season statement and October–December 2026 outlook (30 September 2026); IMD/RMC Chennai bulletins, October 2026; Mission Mausam (Cabinet decision, September 2024); NDMA guidelines on urban flooding. Original analysis by Shanmugam IAS Academy.

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