El Niño-Southern Oscillation (ENSO) Conditions



As of May 9, 2024, the NOAA National Centers for Environmental Prediction's (NCEP) El Niño-Southern Oscillation (ENSO) Alert System remains at El Niño Advisory/La Niña Watch. During April 2024, below-average equatorial sea surface temperatures (SSTs) emerged in small regions of the eastern Pacific Ocean. However, above-average SSTs prevailed across the rest of the equatorial Pacific. The latest weekly Niño index values remained between +0.5°C and +0.8°C in all regions, except for Niño-3 which was +0.3°C. Below-average subsurface temperatures held steady during the month, with negative anomalies extending from the International Date Line to the eastern Pacific Ocean. Low-level wind anomalies were easterly over the western equatorial Pacific, while upper-level winds were near average. Convection was near average overall across the equatorial Pacific and Indonesia. Collectively, the coupled ocean-atmosphere system reflected the continued weakening of El Niño and transition toward ENSO-neutral.


The most recent IRI plume favors an imminent transition to ENSO-neutral. Thereafter, La Niña is expected to develop during July-September 2024 and then persist through Northern Hemisphere Winter. The forecast team continues to favor the dynamical model guidance, which suggests La Niña could form as early as June-August 2024, with higher confidence of La Niña during the following seasons. La Niña generally tends to follow strong El Niño events, which also provides added confidence in the model guidance favoring La Niña. In summary, a transition from El Niño to ENSO-neutral is likely in the next month. La Niña may develop in June-August (49% chance) or July-September 2024 (69% chance).



The latest Columbia Climate School International Research Institute (IRI) for Climate and Society ENSO predictions plume, pictured just above and published on May 20, 2024, 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. As of mid-May 2024, waning El Niño conditions persist in the central-eastern equatorial Pacific Ocean (between 160°E to 160°W), with important oceanic and atmospheric indicators aligning with ENSO-neutral conditions. All models in the IRI ENSO prediction plume forecast ENSO-neutral for May-July 2024, which then persists during the boreal summer seasons of June-August and July-September 2024. La Niña becomes the most probable category in August-October 2024 through January-March 2025.







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