El Niño-Southern Oscillation (ENSO) Conditions



As of November 9, 2023, the NOAA National Centers for Environmental Prediction's (NCEP) El Niño-Southern Oscillation (ENSO) Alert System remains at El Niño Advisory. Above-average sea surface temperatures (SST) across the equatorial Pacific Ocean were indicative of a strong El Niño, with anomalies increasing in the central and east-central Pacific in the past month. The latest weekly Niño index values were: +1.4°C in Niño-4, +1.8°C in Niño-3.4, +2.1°C in Niño-3, and +2.2°C in Niño-1+2. Area-averaged subsurface temperature anomalies increased slightly, associated with the initiation of a downwelling oceanic Kelvin wave, which strengthened above-average subsurface temperatures in the central equatorial Pacific. Low-level wind anomalies were westerly in the east-central Pacific, while upper-level wind anomalies were easterly in the western and central Pacific. Convection/rainfall was enhanced around the International Date Line, extending into the eastern Pacific. Suppressed convection/rainfall strengthened around Indonesia. The equatorial Southern Oscillation Index (SOI) and the station-based SOI remained negative. Collectively, the coupled ocean-atmosphere system reflected a growing El Niño.

The most recent IRI plume favors El Niño to continue through Northern Hemisphere Spring 2024. Based on the latest forecasts, there is a greater than 55% chance of at least a "strong" El Niño (i.e., ≥1.5°C in Niño-3.4 for a seasonal average) persisting through January-March 2024. There is a 35% chance of this event becoming "historically strong" (≥ 2.0°C) for the November 2023-January 2024 season. Stronger El Niño events increase the likelihood of El Niño-related climate anomalies, but do not necessarily equate to strong impacts.

In summary, El Niño is anticipated to continue through the Northern Hemisphere spring (with a 62% chance during April-June 2024).



The latest Columbia Climate School International Research Institute (IRI) for Climate and Society ENSO predictions plume, pictured just above and published on October 19, 2023, shows forecasts made by a set of dynamical and statistical models for SST in the Niño-3.4 region, for nine overlapping three-month periods. The predictions plume indicates a high likelihood of El Niño conditions persisting during the last quarter of 2023 and first quarter of 2024. Specifically, during the rest of boreal autumn, winter and early spring, the probabilities of El Niño range from 100% to 95% (i.e., November 2023-January 2024 and December 2023-February 2024: 100%, January-March 2024: 99%, and February-April 2024: 95%). Thereafter, there is a rapid decrease in the probability of El Niño during boreal spring (March-May: 82%, April-June: 55%, May-July: 34%, and June-August 2024: 22%). The second most probable category throughout the forecast period is ENSO-neutral. ENSO-neutral becomes the most likely category during May-July (58%) and June-August 2024 (56%). The probability that La Niña will redevelop is almost zero during most of the forecast period, but increases to 8% in May-July and 22% in June-August 2024.







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