![]() ![]() Check the probabilities for all El Niño outcomes here and read more about forecasting El Niño here. Another potential, but also less likely, outcome is a weak El Niño, with about a 12% chance. The incredible warmth of the global oceans could throw us a curveball, since we’ve not seen this before. Clearly, we think this is unlikely, but it’s not impossible. While El Niño conditions have developed, there’s still a small chance (4-7%) that things will fizzle out. Bring in the clownsĪs I mentioned above, nature always has surprises in store, and predicting anything several months in advance is difficult. The top two May values were 19, both of which preceded strong El Niño events, but the third, 1980, did not. This definitely isn’t a 100% certain indicator that a strong El Niño will develop, but it is suggestive. In fact, the May 2023 average subsurface temperature was the fourth-warmest May value in our record (1979–2023). ![]() There is currently quite a lot of warmer-than-average water under the surface of the Pacific, as one downwelling Kelvin wave (an area of warm water that sloshes from the west to the east under the surface) has passed through and another is emerging. Graph showing the average temperature over the past year of the top 300 m (~1000 ft) of the Pacific Ocean, 180-100°W departure from the long-term (1991–2020) average. and warmer air to the northern half of North America. For example, in an El Niño winter, an extended North Pacific jet stream tends to bring more storms across the southern tier of the U.S. The Hadley circulation is connected with the jet streams over the middle to high latitudes, which steer storms around the world and separate cold and warm air masses.Īs El Niño heats the atmosphere above the central and eastern tropical Pacific, it leads to a stronger Hadley circulation and changes to the jet streams. ![]() In a one-paragraph nutshell: warm air that rises near the equator moves toward the poles high up in the atmosphere, descending again near 30 °N and 30 °S, in an overturning pattern called the Hadley circulation. ![]() We spend so much time and energy studying and forecasting El Niño (and its counterpart, La Niña) because those changes to the atmospheric circulation have global impacts. Both measured -1.0 standard deviations in May (meaning the indexes were lower than about two-thirds of all measurements), providing significant indication of the weaker Walker circulation and further evidence that the ocean-atmosphere system has coupled and El Niño conditions have developed. We quantify the atmospheric component of El Niño using the Equatorial Southern Oscillation Index ( EQSOI) and the Southern Oscillation Index ( SOI), both of which compare the surface atmospheric pressure in the western Pacific to that in the eastern Pacific (more details on these indexes here). Convection over Indonesia was reduced, too, another characteristic of the weaker Walker circulation. Over the past month, evidence of the weakened Walker circulation appeared in the form of weaker trade winds over the western Pacific and more clouds and rain over the equatorial Pacific. Anomalous ocean warming in the central and eastern Pacific (orange) help to shift a rising branch of the Walker Circulation to east of 180°, while sinking branches shift to over the Maritime continent and northern South America. Generalized Walker Circulation (December-February) anomaly during El Niño events, overlaid on map of average sea surface temperature anomalies. These strong surface winds help to keep the warm water piled up in the western Pacific. The average Walker circulation is characterized by rising air and storms (convection) over the very warm waters of the far western Pacific, west-to-east winds high up in the atmosphere, descending motion over the relatively cooler waters of the eastern Pacific, and the trade winds-east-to-west surface winds. The third criteria, “indications of a weaker Walker circulation,” refers to the average atmospheric pattern over the equatorial Pacific. We anticipate that it will remain above this El Niño threshold for the next several months, based on climate model predictions and current conditions in the tropical Pacific (more on this in a minute)… check! There are the first two of our three rings criteria. NOAA, based on Coral Reef Watch maps available from NOAA View. A higher-resolution version of this animation is available as a movie. The waters in the key monitoring region, which scientists call "the Niño-3.4 region," start out cooler than average (blue) and progressively become warmer than average (red) as La Niña ends and El Niño arrives. Animation of maps of sea surface temperatures in the Pacific Ocean compared to the long-term average over five-day periods from the end of January to early June 2023. ![]()
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