NASA says El Niño on track to surpass 1997 event

NASA sea level satellites show the 2026 El Niño looks a lot like the 1997-98 event, one of the strongest on record, and may end up bigger. NASA Earth Observatory published side-by-side satellite maps on October 23 comparing the two. NASA Earth Observatory "Right now, this one is on track to be even bigger," said Josh Willis, project scientist for sea level missions at NASA's Jet Propulsion Laboratory. Willis added that the pattern's effects on weather this winter are still uncertain.earthdata.nasa.gov

The maps compare sea surface height on October 13, 1997, measured by the TOPEX/Poseidon satellite, with October 12, 2026, measured by Sentinel-6 Michael Freilich. Warm water expands, so higher-than-normal sea levels in the central and eastern Pacific show where El Niño heat is building up. NASA Earth Observatoryearthdata.nasa.gov

A familiar pattern

"What's unique about altimetry is that we have a 35-year record from nearly identical satellites flying almost the same ground track," Willis said. That record "lets us look back in time and compare this El Niño to what happened in 1997." Phys.org The 2026 event came on much faster than the 1997 one. By October, though, the two looked alike. Both show sea level sloping from low in the west to high in the east, and both have warm, high water reaching all the way to South America. NASA Earth Observatoryphys.org+1

The 2015-16 El Niño was also very strong but took a different shape. Less of its warm water reached South America, and its heaviest rain fell over Central America, Mexico and the southeastern United States. Phys.org A separate NASA Earthdata analysis found that the 2026 event started late and at first trailed 1997 and 2015. Eastward wind bursts during the summer then set off new Kelvin waves, which helped it catch up. NASA Earthdataearthdata.nasa.gov+1

Forecasters point to a historic event

NOAA's Climate Prediction Center said on October 8 that a strong-to-very strong El Niño is likely to last through January-March 2027, with odds above 83%. It put an 83% chance on the October-December period passing the strength of every El Niño recorded since 1950. NOAA Climate Prediction Center Columbia University's International Research Institute (IRI) for Climate and Society reported that the weekly Niño 3.4 temperature index reached +3.3°C in mid-October. All 27 models the institute tracks forecast a "very strong" event. IRI The World Meteorological Organization expects tropical Pacific temperatures to run up to 3.8°C above average from November through January. USA Todayusatoday.com+2

Impacts still a "dice roll"

In 1997-98, El Niño brought heavy rain to California and across the southern United States. Willis said impacts this time could be similar. NASA Earth Observatory NOAA's Geophysical Fluid Dynamics Laboratory said the event is nearing its peak. Even so, its effects on the U.S. may keep growing through the winter as the ocean signal fades. NOAA GFDLgfdl.noaa.gov+1

Willis cautioned that El Niño's influence passes through a chaotic atmosphere, and its signal can get muddled outside the tropics. "There's always a bit of a dice roll here," he said. "Just because this El Niño looks like 1997 doesn't mean it will be exactly the same—it's just our best guess at the moment." NASA Earth Observatoryscience.nasa.gov