El Niño years do not always translate into monsoon failure, yet 2026 recorded the lowest rainfall since 2015. Examine the role of ENSO and other ocean-atmosphere drivers in Indian monsoon variability.

The 2026 southwest monsoon ended at 759.4 mm, 87% of the Long Period Average (LPA). This was a 12.6% deficit and the driest season since 2015 [1]. IMD linked it to one of the strongest El Niño events in recent history [1]. ENSO shapes the monsoon, but it works together with other drivers that can either offset it or make it worse.

Role of ENSO

• Mechanism: When the eastern Pacific warms, the Walker circulation shifts east. Air then sinks over India, which weakens convection and the monsoon trough.
• 2026 case: IMD's first-stage forecast on 13 April flagged a subdued season [2]. In May it cut the forecast to 90% of LPA, and the actual 87% fell inside that error band [1].
• Precedent: In 2015, also an El Niño year, rainfall was 758.2 mm, almost the same as 2026 [1].
• Limits: In some strong El Niño years, such as 1997, the monsoon was still normal. ENSO raises the risk of a poor monsoon but does not decide the outcome on its own.

Other ocean-atmosphere drivers

• Indian Ocean Dipole (IOD): A positive IOD, with a warm western Indian Ocean, can cancel out El Niño's effect. A neutral or negative IOD leaves El Niño's effect intact.
• Madden-Julian Oscillation (MJO): This eastward-moving band of convection brings active and break spells within the season. It controls when rain falls rather than how much falls in total.
• Eurasian snow cover and land-sea thermal contrast: Heavy winter snow weakens summer heating of the land, which weakens the monsoon.
• Western disturbances and warming seas: These make rainfall patchier. In 2026 the East and Northeast had their driest monsoon since 1901 [1], so El Niño explains the national total but not the uneven regional pattern.

Pacific warming (El Niño) → Walker cell shifts east → air sinks over India
        ± IOD phase   ± MJO timing   ± Eurasian snow
                          ↓
        Size of the seasonal deficit and where it falls

Fig: Interacting drivers of monsoon variability

Implications

• Forecasting has to combine several indicators. IMD's move from statistical to dynamical (Monsoon Mission) models reflects this.
• With El Niño still strengthening, October rain is forecast below 85% of LPA [1]. This puts rabi sowing at risk.

In short, the monsoon results from several ocean-atmosphere drivers acting together, with ENSO as the most important one. Better district-level extended-range forecasts, faster irrigation expansion under PMKSY, and climate-resilient farming (in line with SDG 13) can turn accurate forecasts into real drought preparedness.