Below-average sea surface temperatures (SSTs) strengthened in the east-central Pacific Ocean during the past month [Fig. 1]. All of the latest weekly Niño index values were near -1.0°C, with the exception of Niño-1+2 which was at -1.8°C [Fig. 2]. Since late July 2022, negative subsurface temperature anomalies have been quite persistent [Fig. 3], reflecting the stationary pattern of below-average temperatures across the eastern Pacific Ocean [Fig. 4]. For the monthly average, low-level easterly wind anomalies and upper-level westerly wind anomalies were evident across most of the equatorial Pacific. However, in the last week, the low-level trade winds weakened in association with sub-seasonal tropical variability. Convection remained suppressed over the western and central tropical Pacific and enhanced over Indonesia [Fig. 5]. Overall, the coupled ocean-atmosphere system continued to reflect La Niña.
The most recent IRI plume forecast of the Niño-3.4 SST index indicates La Niña will persist into the Northern Hemisphere winter 2022-23, and then transition to ENSO-neutral in February-April 2023 [Fig. 6]. The forecaster consensus, which also considers the North American Multi-Model Ensemble (NMME), is in agreement with the timing of this transition. The recent weakening of the trade winds suggest below-average SSTs may be near their minimum, though considerable uncertainty remains over how gradually the anomalies will decay. In summary, there is a 76% chance of La Niña during the Northern Hemisphere winter (December-February) 2022-23, with a transition to ENSO-neutral favored in February-April 2023 (57% chance; [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 8 December 2022.
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