During December, below-average sea surface temperatures (SSTs) weakened over the equatorial Pacific Ocean [Fig. 1]. All of the latest weekly Niño index values were between -0.7°C and -0.8°C [Fig. 2]. The subsurface temperature anomalies also weakened substantially [Fig. 3], but below-average subsurface temperatures persisted near the surface and at depth in the eastern equatorial Pacific Ocean [Fig. 4]. However, the atmospheric circulation anomalies over the tropical Pacific Ocean did not notably weaken. Low-level easterly wind and upper-level westerly wind anomalies remained across most of the equatorial Pacific. Suppressed convection persisted over the western and central tropical Pacific, while enhanced convection was observed around Indonesia [Fig. 5]. Overall, the coupled ocean-atmosphere system continued to reflect La Niña.
The most recent IRI plume predicts that La Niña will transition to ENSO-neutral during the Northern Hemisphere winter 2022-23 [Fig. 6]. Interestingly, the dynamical models indicate a faster transition (January-March) than the statistical models (February-April). At this time, the forecaster consensus favors the statistical models, with a transition to ENSO-neutral in the February-April 2023 season. The sustained atmospheric circulation anomalies and the weakening downwelling oceanic Kelvin wave do not support an imminent transition. However, lower accuracy during times of transition, and when predictions go through the spring, means that uncertainty remains high. In summary, a transition from La Niña to ENSO-neutral is anticipated during the February-April 2023 season. By Northern Hemisphere spring (March-May 2023), the chance for ENSO-neutral is 82% [Fig. 7].
This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA's National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Additional perspectives and analysis are also available in an ENSO blog. A probabilistic strength forecast is available here. The next ENSO Diagnostics Discussion is scheduled for 9 February 2023.
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