El Niño excepcional

El Niño strengthened further over the past month, with sea surface temperature anomalies exceeding +3.0°C in the eastern equatorial Pacific. Except for the Niño-4 index, which decreased to +0.1°C in August, values in the other Niño indices increased, reaching +1.8°C in Niño-3.4, +2.5°C in Niño-3, and +3.4°C in Niño-1+2. The equatorial subsurface temperature index (average from 180°-100°W) remained steady during August, reflecting a deeper-than-average thermocline. Subsurface temperatures continued to be significantly above average, with widespread anomalies in excess of +10.0°C at depth. Low-level westerly wind anomalies and upper-level easterly wind anomalies extended from the western to the east-central equatorial Pacific. Enhanced convection and rainfall persisted from the central to the eastern Pacific, while anomalies remained suppressed over Indonesia. The traditional and equatorial Southern Oscillation indices remained negative. Collectively, the coupled ocean-atmosphere system reflected a strengthening El Niño.

The CPC Official ENSO outlook, which synthesizes multiple models from North America and abroad, indicates El Niño will continue to strengthen through the end of the year. During the October-December 2026 season, there is a 75% chance of a historic event that would exceed the strength of previous El Niño events dating back to 1950 (+2.5°C or more for a 3-month RONI value). With an event of this magnitude, the chances of experiencing impacts consistent with El Niño are larger, though not guaranteed (see CPC outlooks for probabilities of seasonal anomalies). In summary, El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter 2026-27.