Extreme Spring Pacific Annular Warming Elevates the 2026/27 El Niño

Strong sea surface temperature anomalies were observed in the western, northeastern, and southeastern tropical Pacific in spring 2026, forming a rare and extreme annular warming pattern in the tropical Pacific over the past 40 years. Meanwhile, the upper ocean heat content in the equatorial Pacific has turned positive, seemingly ready to boost an El Niño toward the end of 2026. Using a state-of-the-art climate prediction system, we show that if the current heat content buildup leads to a moderate 2026/27 El Niño, the extreme spring annular warming pattern is highly likely to elevate it to a super El Niño. While the impact of the annular warming is insensitive to initial conditions in the model, inter-basin remote forcing and high-frequency perturbations may introduce uncertainties into our prediction.