NASA Earth Observatory published a comparison on October 23, 2026, showing that the Pacific sea-surface-height pattern mapped on October 12, 2026, closely resembled the pattern mapped on October 13, 1997. In both, elevated water stretched across the central and eastern equatorial Pacific toward South America. NASA says the resemblance describes an ocean pattern; regional weather depends on how the atmosphere responds, too.
Three maps, three satellite missions
NASA’s comparison pairs each observation with a specific satellite mission. The 2015 map offers a useful contrast: elevated water reached the South American coast less extensively than in the 1997 and 2026 maps.
| Map date | Satellite data source | Pattern NASA describes |
| October 13, 1997 | TOPEX/Poseidon | Elevated water extended across the Pacific toward South America. |
| October 12, 2015 | Jason-2 | Elevated water reached the South American coast less extensively. |
| October 12, 2026 | Sentinel-6 Michael Freilich | The pattern closely resembled October 1997, with elevated water extending toward South America. |
NASA says the 2026 El Niño developed more suddenly than the 1997–98 event, even though their October maps look similar. The satellite record behind these comparisons spans 35 years. NASA/JPL scientist Josh Willis says successive missions overlap, with nearly identical satellites flying almost the same ground track.
How sea-surface height indicates ocean heat
Satellite altimetry measures sea-surface height. Warmer water expands, so higher-than-normal sea levels in the central and eastern equatorial Pacific indicate a buildup of heat associated with El Niño. NASA removed seasonal cycles and long-term trends from the maps to emphasize shorter-term changes.
Why a similar ocean pattern does not settle regional weather
NASA says El Niño’s atmospheric signal can become muddled as it travels beyond the tropics, and regional effects depend on where ocean warming occurs and how the atmosphere responds. A close match between ocean maps therefore does not guarantee that 2026 will bring the same weather impacts as 1997.
The earlier events had different rainfall patterns. NASA describes heavy rain in California and the southern United States during 1997–98. During 2015–16, rainfall was concentrated more over Central America and the southeastern United States, with significant flooding in Mexico. Those histories provide context for the maps, not a forecast for the United States in 2026.
NOAA’s October 8, 2026 outlook, relayed by NASA, gave an 83% chance of strong-to-very-strong El Niño conditions through the first three months of 2027. Josh Willis also said the 2026 event was on track to be bigger than the 1997–98 event.
