El Niño strengthened over the past month, with a large area of sea surface temperature anomalies in excess of +1.0°C across the central and eastern equatorial Pacific [Fig. 1]. The latest weekly Niño-3.4 index value was +1.2°C, with the westernmost (Niño-4) and easternmost (Niño-1+2) indices at +0.5°C and +2.7°C, respectively [Fig. 2]. The equatorial subsurface temperature index (average from 180°-100°W) increased [Fig. 3], as a recent downwelling Kelvin wave deepened the thermocline and raised temperatures in the eastern Pacific [Fig. 4]. Low-level westerly wind anomalies and upper-level easterly wind anomalies were observed over the western and central equatorial Pacific. Convection was enhanced over the central and east-central equatorial Pacific and was suppressed over Indonesia [Fig. 5]. The traditional and equatorial Southern Oscillation indices were significantly negative. Collectively, the coupled ocean-atmosphere system reflected a strengthening El Niño.

The North American Multi-Model Ensemble (NMME) average, including the NCEP CFSv2 [Fig. 6], forecasts El Niño to intensify through 2026. Alongside model forecasts, a strong coupling of the atmospheric and oceanic circulation across the Pacific contributes to very high confidence that El Niño will continue through early 2027 [Fig. 7]. There is an 81% chance of a very strong El Niño during October-December [Fig. 8] that would rank among the largest El Niño events in the historical record going back to 1950. Even the strongest El Niño events do not lead to the typical impact everywhere, but stronger events can more significantly tilt the odds in favor of expected outcomes (see CPC outlooks for probabilities of seasonal anomalies). In summary, El Niño continues and will strengthen through the end of the year, with a 97% chance it will last through early spring 2027.