NASA Tracks May Kelvin Wave in El Niño Southern Oscillation Signal
A warm Kelvin wave reached the Pacific off South America in May, and scientists say the el Niño southern oscillation is likely to produce an El Niño later this year. Sea level data from the Sentinel-6 Michael Freilich satellite showed a swell of warm water hundreds of miles wide off Peru, where seas were more than 5.9 inches higher than long-term averages by mid-May.
Josh Willis, a sea level researcher at NASA's Jet Propulsion Laboratory and project scientist for Sentinel-6 Michael Freilich, said, "While this year's event started a bit later than the big El Niños of 2015 and 1997, it's beginning to catch up." He also said, "We'll see how big it gets."
Sentinel-6 Michael Freilich data
The satellite, launched in 2020 by NASA and led by ESA for the E.U. Copernicus Programme, measures and maps water height for the entire ocean every 10 days down to fractions of an inch. NASA said it uses that record to track massive Kelvin waves as they move across the Pacific, where warm water can accumulate off the shores of Colombia, Ecuador, and Peru over several months.
Several waves of higher, warmer water appeared in 2026 satellite data. A small Kelvin wave formed around Micronesia in late January, dissipated by mid-February, and a new wave emerged in early March before moving east over time. By May, the wave had arrived off the South American coast.
Peru and the Pacific
The warm water off South America is the most immediate sign that El Niño will likely emerge later in the year. Warm Kelvin waves often precede El Niño events, and warmer waters in the central and eastern Pacific can shift the jet stream and change storm tracks worldwide.
El Niño can bring heavy precipitation to some regions and deficits to others. Fishermen in the 1600s coined the name because the pattern tended to intensify around Christmastime, and the same Pacific signal now gives forecasters a measurable head start on what may come next across the ocean basin.
Nadya Vinogradova Shiffer, lead program scientist at NASA Headquarters in Washington, said, "NASA's observation of El Niño uses sea level satellites like Sentinel-6 Michael Freilich to track massive Kelvin waves as they cross the Pacific, capture changes in Earth's ocean thermodynamics, improve forecasts of weather extremes, and help communities prepare for potential coastal hazards." She added, "Stay tuned as more ocean stories continue to unfold."
