La Nina May Wind Down Earlier Than Expected

Key Takeaways:

• La Niña has likely crossed its peak and is now showing early signs of weakening.
• Ocean and atmosphere coupling is slowly degrading, which is needed for La Niña’s collapse.
• MJO is strengthening and moving eastward, supporting cyclone activity near Australia and the South Pacific.
• IOD is expected to remain neutral to slightly negative in 2026, but with low confidence.

Equatorial sea surface temperatures are below average across the east-central and eastern Pacific Ocean. Atmospheric anomalies, though weak, are still consistent with La Niña.

ENSO Alert System Status continues with a La Niña Advisory. The final El Niño Advisory is yet to be issued, which will mark the end of La Niña/El Niño conditions.

The quarterly ONI maintained the threshold value of -0.5°C for two successive quarters: Sep-Oct-Nov and Oct-Nov-Dec. Continuation of El Niño or La Niña needs an intrinsic bonding between atmospheric and oceanic conditions. Side-by-side degradation of both is a prerequisite for the collapse of the event. As per the preliminary precursors, the cold anomalies of the tropical Pacific have started weakening from the west. The atmospheric influence, though lessening, is a slow process.

ENSO: The tropical Pacific has been dominated by a cold phase for the last many weeks, but there are temperature anomalies negating the ocean cool for the last 3–4 weeks. There were fluctuations even during this period, making it difficult to establish a clear pattern. It seems that La Niña has crossed its ‘peak’ and may start weakening. Likely continuation of this trend may lead to an abrupt collapse, a little earlier than expected.

La Niña cooling (Niño 3.4) is visibly peaking in late November and another spike is seen in December, after a dip in between. Off late, the temperature anomaly has started to rise back rapidly. An important change is also occurring deep below the ocean surface. Niño 3.4 anomaly had earlier reached a three-week low of -0.5°C but has sharply changed to -0.8°C in the last observation. This needs to be observed for continuity in the coming weeks.

IOD: The Indian Ocean Dipole has generally remained in a neutral phase for the last about five weeks. December to April is typically an inactive phase for IOD, and the index more often retains the neutral position. However, the IOD has been fluctuating and changing its stance in recent years. The index was significantly negative during 2020–22 and thereafter, contrastingly becoming strongly negative in late 2023. The index remained remarkably negative during monsoon 2025. Models indicate potential for a negative/neutral IOD during 2026, albeit with a fair amount of uncertainty and low confidence in the forecast.

MJO: The Madden–Julian Oscillation was weak and incoherent till the first week of January 2026. However, after a slow start to January, the pulse has recently emerged from the unit circle over the Western Pacific in Phase 6. With the disruption of enhanced trade winds across the equatorial Pacific, La Niña conditions are weakening. With this, the dynamical models are indicating a good increase in the RMM index and suggesting its eastward propagation towards the Western Hemisphere by week-3. This will favour tropical cyclone formation along the northern coast of Australia and the South Pacific. Even the Western Pacific will remain inclined for a storm, though tropical cyclones tend to be rarer in the Northern Hemisphere during boreal winters.

Overall, La Niña conditions appear to be weakening. The collapse of La Niña, a little before time, may follow a major Pacific flip to reset the weather pattern across the globe.