Wicked surprise

1. At a Glance

• The northeast monsoon (NEM), also called the "other monsoon", brings rain from October to December. It is concentrated over the south-east peninsula: Tamil Nadu, Puducherry, coastal Andhra Pradesh, Rayalaseema, south interior Karnataka and Kerala [1][3].
• The editorial says the NEM contributes only around a quarter of India's annual rainfall. It is still the main rain season for the south-east coast [1].
• The core UPSC point is that the NEM is harder to forecast than the southwest monsoon (SWM). IMD's seasonal "normal" band for the NEM is ±12%, against ±5% for the SWM. That wide band can hide extreme events like the Chennai deluge of December 1, 2015 [1].
• El Niño connects the two seasons. It is linked to a weak SWM and has been associated with heavy NEM events, as in 2015 and 2023 [1][5][6].

2. Why in the News

• The Hindu editorial "Wicked surprise" (26 Oct 2026, p. 8, Chennai edition) warns that the NEM is unpredictable and that the south must be prepared, especially after a deficit SWM [1].
• SWM 2026 was a deficit season: 759.4 mm against a normal of 868.6 mm, a 12.6% deficit and the driest in 11 years. This hurt kharif sowing and shows up in food inflation [1][4].
• IMD's NEM Seasonal Outlook (1 Oct 2026) forecasts normal Oct–Dec rainfall over South Peninsular India, at 88–112% of the LPA [2].
• NEM onset was declared on 15 Oct 2026, the same time the SWM withdrew from the whole country [4].

3. Background & Evolution

• Conceptually, the NEM is the "retreating" or winter monsoon. Once the SWM withdraws, the wind pattern reverses and brings rain to the south-east coast [1][4].
• 2015: An El Niño year. Nov 2015 saw about 1,200 mm over Chennai, the highest November total in about 100 years. On 1 Dec 2015 about 300 mm fell, the wettest December day on record. More than 500 died and 18 lakh were displaced in Tamil Nadu [1][5].
• Before the 2015 season, IMD had forecast 11–12% above-normal NEM rain for the southern states [5].
• The 2015 rain came in three heavy spells (9 Nov, 16 Nov, 1 Dec). Radar studies show cloudburst-level rates of 100–200 mm/hour over Chennai [7].
• Dec 2023: Severe Cyclone Michaung brought Chennai rainfall comparable to 2015. Later that month an El Niño-fuelled NEM deluge hit south Tamil Nadu [6][8].
• 2026: IMD cut its SWM forecast to 90% of LPA and warned of a 60% chance of deficient rainfall [9]. The season ended 12.6% below normal [1][4].

4. Core Static Facts

5. Multi-Dimensional Analysis

Economic

• The SWM deficit has hit kharif sowing and is feeding food inflation [1].
• A normal NEM would help rabi crops, reservoirs and groundwater in Tamil Nadu and south Andhra Pradesh. The 24% SWM deficit in the South Peninsula makes the NEM more important this year [2].

Environmental / Climatic

• El Niño cuts both ways: it is linked to a weak SWM, and El Niño years such as 2015 and 2023 have produced extreme NEM rain [1][5][6].
• IMD expects a strong to very strong El Niño to persist through Jan–Mar 2027 [2].
• The 2026 outlook is spatially split: normal to above-normal rain in southern Kerala and Tamil Nadu, below-normal in most other areas, and above-normal temperatures across most of the region [2].

Scientific / Technological

• NEM forecasts are much less precise, with a band of ±12% against ±5% for the SWM [1].
• Season-scale forecasts miss short, intense spells. In 2015, rain fell at 100–200 mm/hour, which shows the need for Doppler radar and nowcasting [7].

Administrative / Disaster Management

• Unplanned urbanisation has destroyed Chennai's natural flood sinks, such as marshlands and river channels [10].
• The cost of the 2015 floods (more than 500 dead, 18 lakh displaced) is the benchmark for urban flood preparedness [1].

Social

• Urban poor living near drainage channels and farmers who depend on rain in the south-east are the most exposed. Displacement on the scale of 2015 strains relief systems [1][10].

6. Recent Developments (last 12–18 months)

• May 2026: IMD revises its SWM forecast down to 90% of LPA, with a 60% chance of deficient rainfall [9].
• Sept 2026: The SWM ends at −12.6%, the driest in 11 years [1][4].
• 1 Oct 2026: IMD issues its NEM Seasonal Outlook, forecasting normal rain (88–112% of LPA) [2].
• ~12 Oct 2026: IMD says NEM onset over the southern peninsula is likely within 2–3 days [3].
• 15 Oct 2026: The SWM withdraws and the NEM sets in over the south-east peninsula [4].
• Mid–late Oct 2026: IMD forecasts a wet spell with isolated heavy rain over the south peninsula until about 21–23 Oct [2][11].
• 26 Oct 2026: The Hindu editorial "Wicked surprise" calls for vigilance [1].

7. Prelims Hooks

• The NEM season runs October–December [1].
• IMD's NEM LPA for South Peninsular India is ~334 mm, based on 1971–2020 [2].
• The NEM "normal" range is 88–112% of LPA [2].
• The SWM forecast error margin is ±5%; the NEM band is ±12% [1].
• The 2026 SWM deficit was 12.6% (759.4 mm vs 868.6 mm), the driest in 11 years [1].
• The NEM set in on 15 Oct 2026, the same day the SWM withdrew [4].
• The 2026 NEM outlook assumes a strengthening El Niño and a neutral IOD [2].
• On 1 Dec 2015, Chennai had about 300 mm, its wettest December day on record [5].
• Nov 2015: about 1,200 mm in Chennai, the highest November total in about a century [5].
• The 2015 floods killed 500+ and displaced 18 lakh in Tamil Nadu [1].
• The NEM region includes Rayalaseema and south interior Karnataka, not just Tamil Nadu [1].
• Cyclone Michaung (Dec 2023) produced Chennai rainfall comparable to 2015 [8].

8. Why a 'Normal' Forecast Can Still Drown Chennai

• The forecast measures the whole season. Floods come from one bad day.
• IMD calls the NEM "normal" if the Oct–Dec total is 88–112% of the LPA (long period average, the average rain over many years). For the South Peninsula, the LPA is about 334 mm [2].
• On 1 Dec 2015, Chennai got about 300 mm in a single day [5]. That is close to 90% of a whole season's normal rain, falling in 24 hours.

• So a season can end up "normal" on paper and still include a day that floods a city.

• The 2015 forecast was not really wrong, and that is the problem

• Before the 2015 season, IMD forecast NEM rain 11–12% above normal [5].
• That told officials it would be a wet season. It said nothing about rain falling at 100–200 mm per hour [7].

• A seasonal forecast cannot do the job of a city warning system. The 2015 disaster happened in the space between the two.

• The 2026 "normal" hides a split map

• The 2026 outlook expects normal to above-normal rain in southern Kerala and Tamil Nadu, but below-normal rain in most other areas [2].
• One regional word, "normal", covers both a flood risk in one place and a dry spell in another. Planners need the district map, not the headline.

9. Was 2015 a Natural Disaster or a Man-Made One?

• The case for 'nature did it'
• The rain really was extreme: the highest November total in about 100 years, and the wettest December day on record [5].
• Radar shows rates of 100–200 mm per hour, which is cloudburst level [7].

• The Tamil Nadu government called it a "rarest of rare natural calamity". It said all water released from Chembarambakkam went through the regulators (the controlled gates), and none flowed uncontrolled over the surplus weirs [14].

• What the CAG found

• The CAG (Comptroller and Auditor General) audited flood management in Chennai for 2011-12 to 2015-16. It called the flood "not a natural disaster" but a man-made one under CWC (Central Water Commission) norms [12][13].

• The CWC test: a flood counts as man-made if a dam releases more water than is flowing into it. On 2 Dec 2015, Chembarambakkam's outflow was higher than its inflow for 13 hours [12].

• How the reservoir decision made it worse

• On 1 Dec 2015, the lake held 3.481 TMC (thousand million cubic feet) against a full capacity of 3.645 TMC. It was nearly full just as the heaviest rain arrived [12].
• The CAG said the level was kept high partly to protect private land in the foreshore (the land along the lake's edge) [12].

• It estimated that a steady 12,000 cusec (cubic feet per second) could have been released earlier, over six hours. Instead, 20,960–29,000 cusec was let out at the peak [12].

• An honest answer: both are true

• The rain was extreme, and no city drains 300 mm in a day without damage. The government's point holds that far.
• But how full the reservoir was kept, and when water was released, decided how many people the rain reached and how fast. Those were human choices.
• Use this in Mains: extreme weather is the hazard. Human decisions turn it into a disaster.

10. Why the Same City Floods and Then Goes Thirsty

• Flood water went to the sea, not into storage
• From 17 Nov to 10 Dec 2015, 8.7 TMC was released from Chembarambakkam into the sea [12].
• That is more than 75% of the combined capacity of all four reservoirs in the Chennai Metropolitan Area [12].

• A city that depends on the NEM for water lost most of a season's storage in three weeks.

• The drains could not carry the water where it needed to go

• The CAG found that storm water drains covered too little of the city because too little money was spent on them. Some were badly designed, and the network had missing links [12][13].

• When a drain stops halfway, water collects in streets instead of reaching a river.

• Building on water channels removed the escape routes

• The CAG faulted CMDA (Chennai Metropolitan Development Authority) for failing to stop large-scale construction along waterways and on water bodies [13].

• This matches the loss of marshlands and river channels that the note already records [10]. The audit makes clear the planning authority failed to enforce the rules, not just that the city grew.

• Why a deficit year raises the risk

• The South Peninsula had 24% less SWM rain than normal in 2026 [2]. Reservoir managers will want to fill tanks to the top while they can.
• A nearly full tank is exactly what forced the sudden large release in 2015 [12].
• So a drought year can quietly make a flood more dangerous.

11. What Has Changed Since 2015, and What Still Must

• Warning tools now exist
• In 2019, the Ministry of Earth Sciences launched CFLOWS-Chennai (Coastal Flood Warning System). It links weather forecasts with storm-surge models and covers about 796 flood scenarios [16].
• By 2026, Chennai also has a real-time flood forecasting system that gives up to 72 hours of warning. It combines five weather models with rain, river and lake-level data, covers 74 watersheds and 989 km of rivers, and advises on reservoir operation. It was built with World Bank funding and help from IIT Madras [17].

• The 2015 gap was a missing link between forecasts and action on the ground. That link now exists in technology. What remains is whether officials act on it.

• Tamil Nadu's Water Resources Department should run reservoirs by the forecast, not the calendar

• The CAG's numbers show the alternative: lower the lake early, with small steady releases, before heavy rain is forecast [12].

• The 72-hour warning from the new system gives enough time to do this [17]. The release decision should be written into rules, so no single officer has to guess under pressure.

• CMDA should enforce the no-build line along waterways

• The CAG blamed weak enforcement, not missing rules, for building on waterways [13].

• Each new structure on a channel narrows the path flood water can take.

• Use the national framework and money already available

• NDMA's Guidelines on Management of Urban Flooding (2010) ask states and urban local bodies to prepare city flood plans [15].
• The Fifteenth Finance Commission set aside funds for integrated flood management in Mumbai, Chennai and Kolkata [15]. The test is whether that money reaches the missing drain links the CAG pointed out.

12. Anchors for Answers

• Data: About 300 mm fell on Chennai on 1 Dec 2015, close to 90% of the South Peninsula's whole-season NEM LPA of ~334 mm [5][2]
• Data: 8.7 TMC was released from Chembarambakkam to the sea between 17 Nov and 10 Dec 2015, more than 75% of the capacity of Chennai's four reservoirs [12]
• Report/Committee: CAG Report No. 4 of 2017, Performance Audit of Flood Management and Response in Chennai and its Suburban Area (tabled 2018). It called the 2015 flood "man-made" under CWC norms [12][13]
• Report/Committee: NDMA Guidelines on Management of Urban Flooding, 2010 [15]
• Scheme: Fifteenth Finance Commission funds for integrated flood management in Mumbai, Chennai and Kolkata [15]
• Scheme: CFLOWS-Chennai (MoES, 2019) and Chennai's real-time flood forecasting system with 72-hour lead time (World Bank, IIT Madras) [16][17]

13. Mains Relevance

• GS-I: Geography, covering important geophysical phenomena and the Indian monsoon mechanism.
• GS-III: Disaster management, covering urban floods. Also agriculture, covering rain-dependent cropping and food inflation.
• Possible questions: 1. "The northeast monsoon is less predictable but no less consequential than the southwest monsoon." Discuss this with reference to forecasting limits and El Niño. (250 words) 2. "Chennai's recurrent floods are as much a failure of urban planning as of meteorology." Critically examine this with reference to 2015 and 2023. (250 words) 3. How does ENSO affect the two Indian monsoon seasons differently? What does this mean for agriculture and water security in South India? (150 words)

14. Related Topics to Study Next

• ENSO (El Niño / La Niña): the main driver for both monsoon seasons [2].
• Indian Ocean Dipole (IOD): an input to IMD's seasonal outlooks [2].
• Withdrawal of the SWM / retreating monsoon: the transition that starts the NEM [4].
• Bay of Bengal cyclones, e.g. Michaung: the main source of extreme NEM rain [8].
• Urban flooding and wetland loss in Chennai: the vulnerability that turns rain into disaster [10].
• IMD forecasting system (LPA, extended range, nowcasting): the basis for the uncertainty figures [2][7].
• Food inflation and kharif output: the economic transmission of a deficient monsoon [1].

15. NCERT Concepts to Revise

• Northeast monsoon (Geography): This is the article's core subject: the October–December rain season over the south-east coast and why it is hard to forecast.
• El Nino (Geography): El Niño weakens the southwest monsoon but has coincided with extreme northeast monsoon rain in 2015 and 2023.
• Retreating monsoon (Geography): The northeast monsoon begins as the southwest monsoon withdraws, so this explains the seasonal transition the article describes.
• Urban flooding (Geography): Chennai's 2015 deluge became a disaster because built-up land, drains and lost wetlands could not take the rain.
• Indian Ocean Dipole (Geography): IMD's 2026 outlook uses a neutral IOD alongside El Niño, and a positive IOD can offset El Niño's effect.
• Weather forecasting (Geography): Explains why seasonal forecasts with a wide ±12% band can miss short, intense spells like the 2015 Chennai rain.

16. Common Errors / Trap Areas

• Thinking El Niño only means drought. It weakens the SWM, but El Niño years such as 2015 and 2023 have brought extreme NEM rain [1][5][6].
• Mixing up the error bands. The NEM band is ±12% (88–112%) and the SWM margin is ±5% [1][2].
• Using the wrong LPA. The NEM LPA is about 334 mm for the South Peninsula, based on 1971–2020. The 868.6 mm figure is the all-India SWM normal [1][2].
• Wrong date for the 2015 peak. The worst single day was 1 Dec 2015, but November 2015 also had record rain [5].
• Treating "the NEM is around a quarter of India's annual rainfall" as settled. This is the editorial's phrasing; check it against IMD climatology before using it as a fixed number [1].