Every member of a 30-run climate model ensemble at a major U.S. government laboratory now projects sea-surface temperatures in the central Pacific will exceed 2 degrees Celsius above normal by fall or early winter, a signal that the next El Niño could reach strong or very strong intensity. If that projection holds, the consequences would ripple across continents, shifting jet streams, monsoon patterns, and drought and flood risks for billions of people. The last El Niño, in 2023-24, disappointed forecasters by producing far weaker global weather impacts than expected, raising pointed questions about whether this time will be different.
Full model agreement and what it signals for fall 2026
The Seasonal Predictions from the Research Application (SPEAR) system at NOAA’s Geophysical Fluid Dynamics Laboratory has produced a striking result: all 30 ensemble members peak above 2 degrees Celsius in the Niño-3.4 region during the coming fall and early winter. That level of agreement is unusual. Ensemble models deliberately introduce small variations in starting conditions to capture the range of plausible outcomes, so when every run converges on a strong event, the underlying ocean-atmosphere coupling is sending a powerful signal.
The April update from NOAA’s Geophysical Fluid Dynamics Laboratory describes how the SPEAR ensemble has locked onto a robust warming pattern, with each member surpassing the 2-degree threshold that typically delineates a strong El Niño. While the exact peak timing varies slightly among runs, the clustering of outcomes in late boreal fall and early winter suggests a high likelihood that the Pacific will be in a mature warm phase just as the Northern Hemisphere’s cool season begins.
The Climate Prediction Center’s official ENSO outlook provides a complementary perspective. Its probability table shows El Niño as the dominant outcome through the upcoming winter, with the Relative Niño-3.4 Index indicating elevated chances that anomalies will reach at least moderate strength. While the RONI framework stops short of explicitly labeling the event “very strong” at this lead time, the distribution of probabilities leans heavily away from neutral or La Niña conditions during the key December–February window.
NOAA’s Coral Reef Watch program adds another layer of concern. Its ENSO-focused guidance notes that stronger warm events in the tropical Pacific raise the odds of widespread impacts on ocean ecosystems, including extensive coral bleaching in regions that experience prolonged marine heat stress. Those same sea-surface temperature anomalies drive changes in atmospheric circulation, meaning the potential for ecological disruption and unusual weather tends to rise together as the Niño-3.4 index climbs.
For farmers in Southeast Asia bracing for weaker monsoons, emergency managers in drought-prone East Africa, or utility planners along the U.S. Gulf Coast, the distinction between a moderate and a strong event is not academic. A Niño-3.4 anomaly above 2 degrees Celsius historically correlates with amplified shifts in rainfall belts and temperature extremes that affect food production, energy demand, and disaster preparedness budgets. Even if local outcomes never follow a single script, the background risk of disruptive seasons grows when the tropical Pacific warms this much.
Why the 2023-24 El Niño’s weak teleconnections complicate the forecast
The 2023-24 El Niño reached strong levels in the tropical Pacific, yet its fingerprint on weather outside the tropics was surprisingly faint. A peer-reviewed study published in Communications Earth and Environment found that the event exhibited unusually weak extratropical teleconnections, meaning the expected chain of atmospheric responses that typically carry El Niño’s influence into midlatitude storm tracks and temperature patterns did not fully materialize. That disconnect left parts of North America and Europe with winter weather that bore little resemblance to a textbook strong El Niño season.
Teleconnections are the atmospheric bridges through which tropical Pacific warming reshapes weather thousands of miles away. During a strong El Niño, warmer water shifts tropical convection eastward, which in turn alters the position and strength of the subtropical jet stream. Those changes then cascade into midlatitude circulation patterns, typically producing a wetter-than-normal winter across the southern United States and drier conditions in parts of Australia and Indonesia. A broad body of ENSO research documents how sea-surface temperature and rainfall anomalies translate into these global circulation shifts, while also noting that background climate conditions and competing ocean signals can dampen or redirect the expected patterns.
The 2023-24 outcome raises a direct question for the coming event: if SPEAR’s full-ensemble convergence above 2 degrees Celsius holds through the next several monthly updates, will the Northern Hemisphere atmospheric response actually match the strength of the tropical forcing? One testable expectation is that 500-hectopascal height anomalies during December through February would exceed those observed in the 2023-24 winter by a wide margin, given the projected intensity. But the recent precedent of a strong tropical signal failing to produce proportional extratropical effects means forecasters cannot simply assume a replay of classic El Niño winters like 1997-98 or 2015-16.
Several hypotheses have been advanced to explain why a robust warm event might generate muted teleconnections. Internal atmospheric variability can, by chance, oppose the patterns El Niño would normally favor, especially over the North Atlantic and Eurasia. Other ocean basins, such as the tropical Indian and Atlantic, can also exert their own influences, sometimes reinforcing and sometimes counteracting Pacific-driven changes. On top of that, long-term climate change is altering baseline temperature gradients and jet stream behavior, potentially modulating how El Niño’s signal propagates into higher latitudes.
Open questions and what to watch through summer
Several gaps in the evidence keep the forecast from being definitive. The CPC has not yet released a post-June RONI strength-probability table that would quantify very-strong odds on a month-by-month basis, leaving some uncertainty about just how far above 2 degrees Celsius the Niño-3.4 index might climb. Updated plume graphics from the North American Multi-Model Ensemble and verification data from the latest SPEAR run would help clarify whether the tight ensemble agreement is strengthening or beginning to loosen. Without those updates, the current picture relies heavily on a single month’s model output and the broader probabilistic guidance.
The physical mechanisms that muted the 2023-24 teleconnections also remain an active research topic. If internal atmospheric variability played an outsized role, then the next strong El Niño could still produce a far more canonical pattern of rainfall and temperature anomalies. If, instead, structural changes in the climate system are systematically weakening the bridge between the tropics and the extratropics, forecasters may need to recalibrate how much confidence they place in historical analogs when a new strong event develops.
Over the next few months, several indicators will help clarify which path the climate system is taking. Subsurface temperature profiles across the equatorial Pacific will reveal whether the warm water volume needed to sustain a very strong event is continuing to build or starting to disperse. Trade wind strength and the frequency of westerly wind bursts will show whether the atmosphere is reinforcing the developing El Niño or allowing it to stall. And as boreal autumn approaches, early signs of jet stream reconfiguration in reanalysis data will offer the first hints about whether teleconnections are likely to resemble the subdued 2023-24 pattern or something more dramatic.
For now, the convergence of a fully aligned SPEAR ensemble, elevated El Niño probabilities from the Climate Prediction Center, and heightened ecological risk highlighted by Coral Reef Watch all point toward a high-impact warm event in the making. Yet the memory of the last winter’s underwhelming extratropical response is a reminder that even the strongest signals in the tropical Pacific do not guarantee specific outcomes far afield. As new data arrive through summer and early fall, the key challenge for forecasters will be balancing the compelling model guidance with the humility earned from recent surprises.
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*This article was researched with the help of AI, with human editors creating the final content.
