NASA satellite observations indicate that the El Niño developing in 2026 could rival some of the strongest events recorded over the past three decades. By comparing ocean surface height measurements from October 1997 and October 2026, scientists have identified similarities that could offer clues about the weather impacts expected in the coming months.
El Niño is a naturally occurring climate pattern that develops roughly every two to seven years. It involves warmer-than-normal water across parts of the equatorial Pacific Ocean and can disrupt weather patterns worldwide. Previous strong events, particularly those in 1997-98 and 2015-16, were associated with wildfires in Indonesia and the Amazon, drought-related crop failures in southern Africa, and heavy rainfall and coastal flooding in Southern California.
According to Josh Willis, project scientist for sea level missions at NASA’s Jet Propulsion Laboratory (JPL), each El Niño develops differently depending on where warm water accumulates in the Pacific and how the atmosphere responds.
“The search for the ‘typical’ El Niño is very elusive,” Willis said. “They’re all different in terms of where they land and how their impacts play out.”
How Satellites Track El Niño’s Development
El Niño develops through interactions between the ocean and the atmosphere. Under normal conditions, trade winds push warm surface water towards the western Pacific, where sea levels are higher than in the east. When these winds weaken, warm water moves eastward, further weakening the winds and sometimes reversing their direction. This feedback loop allows more warm water to accumulate in the central and eastern Pacific.
NASA uses satellite altimetry to measure changes in sea surface height, helping scientists track the movement and accumulation of warm water. As seawater warms, it expands, contributing to higher-than-average sea levels. These changes provide an indicator of the heat building up across the equatorial Pacific.
The October 13, 1997, map was created using data from the TOPEX/Poseidon satellite, while the October 12, 2026, map uses observations from the Sentinel-6 Michael Freilich satellite. Scientists at JPL processed the data, removing seasonal variations and long-term trends to highlight short-term sea level anomalies associated with El Niño and other natural phenomena.
The resulting maps use red to indicate higher-than-average sea levels, white for near-normal conditions and blue for lower-than-average levels.
Willis said the satellite record is particularly valuable because it spans 35 years and includes missions that overlap and follow nearly identical ground tracks.
“What’s unique about altimetry is that we have a 35-year record from nearly identical satellites flying almost the same ground track, with each mission overlapping the next,” Willis said. “That lets us look back in time and compare this El Niño to what happened in 1997. And right now, this one is on track to be even bigger.”
How the 2026 Event Compares With 1997 and 2015
Although the 2026 El Niño developed more suddenly than the 1997-98 event, satellite observations show similarities in their structure. Both display lower sea levels in the western Pacific and elevated sea levels extending eastward towards South America.
These similarities suggest that the two events could produce comparable weather impacts. During the 1997-98 El Niño, for example, California and the southern United States experienced substantial rainfall.
The powerful 2015-16 El Niño, however, developed a different pattern. Satellite maps from October 2015 show that the exceptionally warm water along the equator did not extend towards the South American coast as strongly as it did in 1997 and 2026.
That difference was associated with a different distribution of rainfall during the winter of 2015-16. Impacts were concentrated more heavily over Central America and the southeastern United States, while Mexico experienced significant flooding.
The comparison highlights why the strength of an El Niño alone cannot fully predict its consequences. The location of elevated sea levels and the distribution of warm water across the Pacific also influence how the event affects regional weather.
Strong El Niño Conditions Expected to Continue Into 2027
The US National Oceanic and Atmospheric Administration’s October 8, 2026, outlook estimated an 83 percent chance that a strong-to-very strong El Niño would persist through the first three months of 2027.
However, scientists caution that the eventual impacts of the 2026-27 winter remain uncertain. El Niño influences weather through the atmosphere, a complex and chaotic system in which climate signals can become less clear as they spread beyond the tropics.
Willis warned against assuming that the similarities with 1997 guarantee identical outcomes.
“There’s always a bit of a dice roll here,” Willis 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.”
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