El-NINO UPDATE

ENSO Alert System Status: La Niña Advisory

Synopsis:  La Niña is favored to continue for the next month or two, with a transition to ENSO-neutral most likely in January-March 2026 (68% chance).

La Niña persisted in November, as indicated by the continuation of below-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean [Fig. 1]. The latest weekly Niño-3.4 index value was -0.5°C, with the other Niño index values between -0.2°C and -0.4°C [Fig. 2]. Recent negative subsurface temperature anomalies weakened slightly (averaged from 180°-100°W; [Fig. 3]), but below-average temperatures continued from the surface to 200m depth in the eastern half of the equatorial Pacific [Fig. 4]. The tropical atmosphere reflected La Niña, with low-level easterly wind anomalies evident in the central Pacific and upper-level westerly wind anomalies observed across most of the equatorial Pacific Ocean. Enhanced convection persisted over Indonesia and suppressed convection was near the Date Line [Fig. 5]. The traditional and equatorial Southern Oscillation indices were positive. Collectively, the coupled ocean-atmosphere system remains consistent with La Niña.

The IRI multi-model predictions indicate La Niña will continue in the December-February (DJF) 2025-26 season, but then ENSO-neutral is favored for January-March (JFM) 2026 [Fig. 6]. Together with the North American Multi-Model Ensemble, the team continues to slightly support a weak La Niña through DJF (54% chance), before transitioning to ENSO-neutral in JFM. Even after equatorial Pacific SSTs transition to ENSO-neutral, La Niña may still have some lingering influence through the early Northern Hemisphere spring 2026 (e.g., CPC’s seasonal outlooks). In summary, La Niña is favored to continue for the next month or two, with a transition to ENSO-neutral most likely in January-March 2026 (68% chance; [Fig. 7]).