El Nino Winter 2026-27 — NOAA Puts Very Strong Event Above 90%, With a 69% Chance of a Record Since 1950

NOAA's Climate Prediction Center issued its most recent ENSO Diagnostic Discussion on 13 August 2026 with the ENSO Alert System Status set to El Nino Advisory, the designation used when El Nino conditions are observed and expected to continue. The synopsis is unusually direct: El Nino is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter of 2026-27. Underlying that assessment, the July Nino-3.4 index value came in at +1.4 degrees Celsius, sea surface temperatures were above average across the east-central and eastern equatorial Pacific, and the atmospheric circulation anomalies over the equatorial Pacific were consistent with El Nino — the coupling between ocean and atmosphere that distinguishes a genuine ENSO event from a transient warm anomaly. The most striking number in the discussion concerns the upper tail. For the October-December 2026 season, CPC puts a 69% chance on what it calls a historic event: a three-month Relative Oceanic Nino Index value of +2.5 degrees Celsius or higher, which would exceed the strength of every El Nino in the record dating back to 1950. RONI is a comparatively recent refinement that subtracts the broader tropical-mean warming trend from the Nino-3.4 anomaly, so a record by that measure is a claim about the event's dynamical strength rather than an artifact of a warming background ocean.^[1][2]

The confidence in the CPC statement is echoed by NOAA's Geophysical Fluid Dynamics Laboratory, which published its August 2026 El Nino predictions on 6 August. Running the SPEAR coupled prediction system, GFDL reported that all 30 ensemble members produce a peak El Nino strength that will compete with the strongest events in the historical record. Two features of that forecast matter for interpretation. First, the spread among the 30 members is narrow, which indicates the models are not merely averaging to a strong outcome while disagreeing sharply among themselves. Second, the August forecast is consistent with the July forecast, so the signal has persisted across an initialization cycle rather than appearing once and then drifting. GFDL characterizes this as high confidence and relatively low uncertainty. On timing, the event is expected to peak sometime between October and January, which is typical for ENSO — the coupled ocean-atmosphere system in the tropical Pacific tends to lock to the seasonal cycle and reach maximum amplitude near the boreal winter solstice. That peak window overlaps the October-December season for which CPC assigns the 69% record probability, and it means the strongest ocean signal will be in place before the North American winter storm track has fully responded. Separately, CPC's ENSO strength probability tables put roughly a 63% chance on Nino-3.4 sea surface temperatures exceeding +2.0 degrees Celsius, the conventional threshold for classifying an event as very strong.^[3][4][5]

It is worth being careful about the distinction between an ENSO forecast and a seasonal weather outlook. The ENSO Diagnostic Discussion forecasts the state of the tropical Pacific; it does not forecast snowfall in any particular city. CPC states explicitly in the discussion that when an event of this magnitude is expected, the chances of experiencing impacts consistent with El Nino are larger, but they are not guaranteed, and it directs readers to its seasonal outlooks for probabilities of temperature and precipitation anomalies. With that caveat, the seasonal guidance circulating in late August 2026 pointed in the canonical El Nino direction for North America: wetter-than-normal conditions favored across much of the southern tier of the United States, drier conditions favored across parts of the Pacific Northwest and the north-central states, and above-normal temperatures favored across much of the West, the northern tier and parts of the East for December 2026 through February 2027. Teleconnections — the mechanism by which a tropical Pacific anomaly reshapes the mid-latitude jet stream — were described as ramping up through fall 2026 and strengthening into winter, with the highest precipitation probabilities over parts of the Southeast. Readers tracking this should watch two calendar items. The next ENSO Diagnostic Discussion is scheduled for 10 September 2026, and NOAA separately issues its formal seasonal Winter Outlook in the autumn; in recent years that release has fallen on the third Thursday of October, though NOAA had not published a specific 2026 date as of late August.^[1][2][4]