\n<\/p>\n
El Ni\u00f1o is part of a natural climate pattern that occurs roughly every two to seven years, bringing warmer-than-normal water to parts of the equatorial Pacific. The most recent very strong<\/a> El Ni\u00f1o<\/a> events, in 1997-98 and 2015-16, upended weather patterns. Impacts spanned the planet, from fires in Indonesia<\/a> and the Amazon, to crop failures due to drought in southern Africa<\/a>, to heavy rain<\/a> and coastal flooding in Southern California. The current El Ni\u00f1o<\/a> rivals these past heavyweights.<\/p>\n Every El Ni\u00f1o grows from a feedback loop between the atmosphere and the ocean. Trade winds normally keep warm water piled up in the western Pacific, where it stands higher than in the east. When those winds weaken, that warm water begins to pulse eastward, which further weakens and sometimes reverses the winds, allowing even more warm water to move east. The cycle intensifies as waters continue to warm and pile up in the central and eastern Pacific.<\/p>\n But each El Ni\u00f1o has its own character, shaped by where in the Pacific the warmth builds and how the atmosphere responds. \u201cThe search for the \u2018typical\u2019 El Ni\u00f1o is very elusive,\u201d said Josh Willis, project scientist for sea level missions at NASA\u2019s Jet Propulsion Laboratory (JPL). \u201cThey\u2019re all different in terms of where they land and how their impacts play out.\u201d<\/p>\n Altimetry satellites can track those differences by measuring the height of the sea surface. Because water expands as it warms, higher-than-normal sea levels in the central and eastern equatorial Pacific signal the buildup of heat associated with El Ni\u00f1o. The maps above depict\u00a0sea surface height<\/a>\u00a0anomalies across the Pacific Ocean on October 13, 1997 (left), and on October 12, 2026 (right). Data are from the TOPEX\/Poseidon<\/a> satellite and the\u00a0Sentinel-6 Michael Freilich<\/a> satellite, respectively, and were processed by scientists at JPL.<\/p>\n Shades of red indicate where sea levels were higher than average. Normal sea level conditions appear white, and lower areas are blue. Signals related to seasonal cycles and long-term trends have been removed to highlight sea level anomalies associated with El Ni\u00f1o and other short-term natural phenomena.<\/p>\n \u201cWhat\u2019s 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,\u201d Willis said. \u201cThat lets us look back in time and compare this El Ni\u00f1o to what happened in 1997. And right now, this one is on track to be even bigger.\u201d <\/p>\n Compared with the 1997-98 event, El Ni\u00f1o in 2026 came on much more suddenly. But as of October, the two events appear similar in character\u2014the tilt of sea level (low in the west and high in the east) and high, warm water extending all the way to South America\u2014so Willis thinks the impacts could be similar as well. In 1997-98, that meant, for instance, lots of rain in California and across the southern tier of the U.S.<\/p>\n The 2015-16 El Ni\u00f1o was another heavy hitter but differed in its character. Sea surface height anomalies on October 12, 2015, based on altimetry data from the Jason-2<\/a>\u00a0satellite, are shown above in context with maps from around the same time in 1997 and 2026. In 2015, the exceptionally warm, high water along the equator didn\u2019t push up against South America to the extent it did in the other years. Rainfall impacts that winter concentrated more over Central America and the southeastern U.S., with significant flooding in Mexico.<\/p>\n NOAA\u2019s El Ni\u00f1o outlook<\/a> on October 8, 2026, called for an 83 percent chance of a strong-to-very strong El Ni\u00f1o through the first three months of 2027. But exactly how the impacts will play out in winter 2026-27 and beyond remains to be seen. Willis noted that El Ni\u00f1o’s influence propagates through a chaotic atmosphere, and the signal can get muddled as it extends beyond the tropics. \u201cThere’s always a bit of a dice roll here,\u201d Willis said. \u201cJust because this El Ni\u00f1o looks like 1997 doesn’t mean it will be exactly the same\u2014it’s just our best guess at the moment.\u201d<\/p>\n NASA Earth Observatory <\/em>maps by Lauren Dauphin, using NASA-SSH<\/a> altimetry data provided by Josh Willis, Severine Fournier, and Kevin Marlis, NASA\/JPL-Caltech. Story by Kathryn Hansen.<\/em><\/p>\n\n