NOAA Warns of Strengthening El Niño With Over 90% Chance of Very Strong Event in 2026-27
NOAA's Climate Prediction Center stated on 13 August 2026 that El Niño was strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter of 2026-27. The advisory, issued in the CPC's latest ENSO discussion, confirms that El Niño conditions are present and expected to continue, building on an El Niño Advisory that was already in effect at the end of July 2026.
The 13 August discussion represents a notable upward revision from the CPC's 9 August forecast, which had placed the probability of a very strong El Niño during October-December 2026 at 81%. Four days later, that figure moved above 90%. The CPC's earlier March 2026 ENSO discussion had forecast a 62% chance of El Niño emergence during June-August 2026 and persistence through at least year-end. At that point, La Niña conditions were still present, continuing from February 2026. The trajectory from La Niña to a potentially very strong El Niño within roughly six months aligns with the rapid ENSO transition dynamics that forecasters had flagged in the spring.
The World Meteorological Organization had been tracking the same evolution. In an April 2026 update, the WMO signaled an El Niño event was likely to develop from mid-2026, with implications for global temperature and rainfall patterns. By its May 2026 El Niño/La Niña Update, the WMO set El Niño probabilities at 80% for June-August 2026, with ENSO-neutral likelihood diminished to 20%. A June 2026 WMO update confirmed that 80% likelihood and noted probabilities for continuation through at least November near or above typical thresholds. On 31 July 2026, the WMO reported that a strong El Niño was developing and expected to intensify during August-October 2026, with above-normal temperatures expected worldwide.
NOAA's 13 August forecast supersedes the earlier 81% probability figure from 9 August, and both supersede the WMO's July characterization of a "strong" event in development. The terminology matters: a "very strong" El Niño, as defined by the Oceanic Niño Index, requires a three-month running mean of sea surface temperature anomalies in the Niño 3.4 region at or above 2.0°C. The CPC's latest discussion places the odds of reaching that threshold above 90% for the upcoming fall and winter, a probability assignment that, if realized, would place the 2026-27 event among the most intense ENSO episodes in the observational record.
The broader context here involves the cascade of global teleconnections that a very strong El Niño sets in motion. Warm-phase ENSO events of this magnitude reorganize atmospheric circulation patterns across the Pacific basin and beyond, shifting convection away from the Maritime Continent toward the central and eastern equatorial Pacific. The downstream effects span winter precipitation regimes across the southern tier of the United States, drought risk in the Western Pacific and parts of Australia, and temperature anomalies across North America and Eurasia. The WMO's July warning about above-normal temperatures worldwide intersects with the baseline warming trend, meaning that El Niño's additive effect on global mean surface temperature could push seasonal temperature anomalies higher than they would be under ENSO-neutral conditions.
For commodity markets, agricultural supply chains, and disaster risk management agencies, the forecast window matters. The CPC's October-December target period for peak intensity corresponds to the Northern Hemisphere fall harvest and the Southern Hemisphere planting season. Grain, oilseed, and tropical commodity producers in ENSO-sensitive regions will be pricing in yield risk based on these probability assessments. Energy markets also factor El Niño into winter heating demand forecasts for the Northern Hemisphere.
The forecasting confidence level also warrants attention. A probability above 90% for a very strong event in early August reflects strong model agreement across both dynamical and statistical ENSO prediction systems. That said, the spring predictability barrier, which historically degrades ENSO forecast skill for target periods beyond the boreal spring, is now well in the rearview mirror. August forecasts benefit from more robust ocean-atmosphere coupling signals, including the Bjerknes feedback, which tends to reinforce and sustain developing El Niño conditions through the fall and winter. The rapid upward revision between 9 and 13 August suggests that subsurface heat content and surface wind stress observations are aligning with model trajectories pointing toward peak intensity.
The 2026-27 El Niño follows a La Niña episode that persisted into early 2026, meaning the tropical Pacific has undergone a full-phase transition within a single calendar year. The WMO and NOAA are now in agreement not only on the event's existence but on its likely intensity category, though NOAA's probability for a very strong event exceeds the WMO's July characterization. The next CPC ENSO discussion, typically issued on the second Thursday of each month, will provide an updated read on whether the ocean-atmosphere system continues to reinforce the trajectory forecasters have identified.
