Satellite Finds Warm Pacific Wave Off South America, Reinforcing Likely El Niño in 2026

New satellite measurements have captured a large pulse of warm Pacific water reaching the west coast of South America, giving fresh observational support to forecasts that El Niño is likely to develop later in 2026.

NASA’s Jet Propulsion Laboratory said Wednesday that the Sentinel-6 Michael Freilich satellite observed a warm-water Kelvin wave moving eastward across the equatorial Pacific and arriving off South America in May. By mid-May, seas around Peru were more than 5.9 inches, or 15 centimeters, above long-term averages, NASA said.

That matters because warm water expands. When sea surface height rises in this way, it is a direct sign that the ocean is storing extra heat. A Kelvin wave is an eastward-moving pulse of unusually warm water in the equatorial Pacific. As it travels, it can deepen the thermocline — the boundary between warm surface water and colder deep water — and raise sea level where it arrives. NASA described warm Kelvin waves as a known precursor to El Niño, the climate pattern that can alter rainfall and temperature worldwide.

According to NASA, a small Kelvin wave formed around Micronesia in late January and dissipated by mid-February. A new wave emerged in early March, then moved steadily east and reached the South American coast by mid-May. Sentinel-6 Michael Freilich maps ocean height across the globe every 10 days, down to fractions of an inch, allowing scientists to track such waves across the Pacific.

The satellite observations add weight to forecasts from operational climate agencies, even though El Niño had not yet formally arrived in NOAA’s latest monthly update. In its May 14 ENSO Diagnostic Discussion, NOAA’s Climate Prediction Center said conditions were still ENSO-neutral but issued an El Niño Watch. The center said, “El Niño is likely to emerge soon (82% chance in May-July 2026) and continue through Northern Hemisphere winter 2026-27 (96% chance in December 2026-February 2027).” The International Research Institute for Climate and Society said May 19 that El Niño had about a 98% probability for May-July 2026, with very high odds of lasting through the rest of 2026 and into early 2027.

Forecasters are also stressing caution. NOAA said there is still substantial uncertainty about how strong the event might become. That means El Niño is the most likely outcome, but not every detail of its eventual peak is known.

Even so, the expected shift is already influencing real-world forecasts. NOAA’s May Atlantic hurricane outlook projected a below-normal season and cited expected El Niño conditions as one reason. El Niño often increases upper-level winds over the Atlantic, which can make it harder for storms to organize.

The broader stakes extend well beyond the tropics. El Niño can reshape weather patterns around the world, bringing major swings in rainfall and temperatures and affecting seasonal outlooks months in advance. NASA said the timing of this year’s development is later than in the major 1997 and 2015 El Niño events, but the recent warming wave suggests the Pacific is moving in that direction.

“While this year’s event started a bit later than the big El Niños of 2015 and 1997, it’s beginning to catch up,” said Josh Willis, a Jet Propulsion Laboratory scientist and Sentinel-6 project scientist. “We’ll see how big it gets.”