Somewhere beneath the surface of the equatorial Pacific, a massive pulse of warm water is sliding eastward. It has been building for weeks, fed by westerly wind bursts that shove heat away from the western Pacific warm pool and toward the Americas. By late May 2026, that subsurface signal had grown strong enough to push NOAA’s Climate Prediction Center to a striking forecast: the probability of a very strong, or “super,” El Niño peaking between November 2026 and January 2027 now sits near 50 percent, roughly double where it stood earlier this spring.
If the event reaches that intensity, it would join a short list that includes only 1997–98 and 2015–16, both of which reshaped weather patterns across the globe, drove catastrophic flooding in some regions, deepened drought in others, and helped push global average temperatures to new highs. The 2023–24 El Niño, which contributed to Earth’s hottest year in the modern record, was classified as strong but fell short of the “very strong” threshold. What NOAA is now tracking has the potential to surpass it.
Where the 50 percent figure comes from
The number originates in the CPC’s ENSO Strength Probabilities table, updated in May 2026. That table assigns numeric odds to each intensity category for every overlapping three-month season through the next year. For the November-December-January window, the “very strong” category now carries a probability near 50 percent.
The CPC’s accompanying long-range forecast discussion lays out the physical reasoning. Forecasters point to three converging drivers: subsurface temperature anomalies well above normal, persistent westerly wind anomalies across the western and central Pacific, and a series of downwelling Kelvin waves that are transporting that warmth toward the surface in the central and eastern basin. These are the same mechanisms that loaded the gun before the two previous super events, though the CPC is careful to note that sustained accumulation over several months, not just a promising start, is what separates a very strong El Niño from a moderate one.
A second, independent line of support comes from NOAA’s Geophysical Fluid Dynamics Laboratory. GFDL’s SPEAR seasonal prediction system, running on a separate codebase from the CPC’s operational model suite, published its own April 2026 outlook projecting elevated probability of El Niño onset by summer and continued strengthening into early winter. When two modeling frameworks built on different assumptions converge on a similar trajectory, forecasters treat that as a meaningful boost in confidence.
A new yardstick for measuring El Niño
One technical shift makes this cycle’s numbers different from past forecasts. The CPC has retired the legacy Oceanic Niño Index and replaced it with the Relative Oceanic Niño Index, or RONI, for real-time ENSO classification. The old index compared sea surface temperatures in the Niño-3.4 region against a rolling 30-year average, but decades of ocean warming had been quietly inflating that baseline, making it harder to tell whether the Pacific was genuinely in El Niño mode or simply reflecting a warmer planet.
RONI solves the problem by measuring Niño-3.4 anomalies against the broader tropical ocean belt rather than against its own recent history. The result is a cleaner signal. Every probability figure NOAA now publishes, including the 50 percent super-event estimate, is calibrated to this updated index.
Why 50 percent is not a guarantee
A coin flip is not a certainty, and forecasters are emphatic about the other side of the odds. GFDL’s SPEAR discussion highlights the role of chaotic variability in the coupled ocean-atmosphere system. A few poorly timed easterly wind surges over the next two to three months could stall the Kelvin wave train, cap surface warming in the Niño-3.4 region, and leave the event well short of the very strong threshold, even with the impressive subsurface heat already in place.
There is also a minor discrepancy in NOAA’s own paperwork. The forecast discussion references “ENSO Strength Probabilities issued in April 2026,” while the probabilities page itself carries a May 2026 header. Whether this reflects a routine monthly update or a meaningful upward revision between April and May is not explained. Planners should treat the near-50-percent figure as the most current official estimate while expecting the next monthly update to refine it.
International forecasting agencies, including the World Meteorological Organization, Australia’s Bureau of Meteorology, and Japan’s Meteorological Agency, have not yet published probability estimates that can be directly compared to NOAA’s super-event figure. That does not undermine the CPC’s analysis, but it means the estimate has not been cross-checked against international model ensembles that sometimes diverge from U.S. forecasts at long lead times. Those agencies typically update their ENSO outlooks on monthly cycles, so corroborating or conflicting numbers should emerge in the weeks ahead.
What a super El Niño would actually do
The two previous very strong events offer a rough template, though no two El Niños play out identically. In 1997–98 and 2015–16, the Southern United States and California experienced prolonged, heavy rainfall and severe flooding. Parts of the Pacific Northwest and the Ohio Valley, meanwhile, saw drier-than-normal winters. Globally, coral reefs bleached on a massive scale, agricultural output shifted in South America and Southeast Asia, and energy demand spiked in regions hit by unusual cold or heat.
The economic ripple effects were broad. Commodity markets for grain, coffee, and palm oil swung on production disruptions. Insurers absorbed billions in flood and storm claims. Energy traders repriced natural gas and heating oil futures as winter demand forecasts shifted.
For the current cycle, NOAA has not yet issued specific regional outlooks tied to the super-event scenario. Until those seasonal forecasts arrive, planners are working from historical analogs rather than tailored 2026 guidance. That is a meaningful gap: the U.S. climate landscape has changed since the last super event, with more people living in flood-prone coastal areas, aging levee systems under greater stress, and Western water reservoirs operating under tighter allocation rules.
What communities and households can do now
Flood-control districts along the Gulf Coast and in Southern California have a narrow window to accelerate levee inspections, clear drainage channels, and test pump stations before the wet season arrives. Agricultural operations in regions that historically dry out during El Niño years, particularly in the Pacific Northwest and parts of the Northern Plains, should be reviewing water allocation contingencies and considering drought-tolerant crop rotations.
For individual households, the steps are less dramatic but still worth taking before fall: confirming that flood insurance is active and adequate (standard homeowner policies do not cover flood damage), clearing roof gutters and downspouts, testing backup power systems, and reviewing local evacuation routes. El Niño tends to stress the same infrastructure that struggled in past wet winters, so anyone who dealt with basement flooding, road washouts, or power outages during previous events should assume those vulnerabilities could be tested again.
Day-to-day risk communication will come through the National Weather Service, accessible at the NOAA weather portal. ENSO probabilities set the seasonal backdrop, but watches, warnings, and storm-specific outlooks will carry the operational detail that matters when individual weather systems develop.
The indicators to watch this summer
Between now and fall, three signals will determine whether the forecast holds or fades. The first is subsurface heat content in the equatorial Pacific: if the warm anomaly continues to propagate eastward and surface, the event stays on track. The second is the persistence of westerly wind anomalies; if trade winds reassert themselves and blow consistently from the east, they will push warm water back toward the western Pacific and undercut the developing El Niño. The third is the CPC’s monthly probability updates, which will either confirm the current trajectory or begin walking it back.
For now, the forecast amounts to an early warning with teeth. A 50 percent chance of a super El Niño is not a certainty, but it is the highest such probability NOAA has issued this far ahead of a potential peak since the agency began publishing strength-category forecasts. The time to prepare is while the odds are still being calculated, not after the storms arrive.
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*This article was researched with the help of AI, with human editors creating the final content.
