La Niña persisted in January, reflected by below-average sea surface temperatures (SST) anomalies extending from the western to east-central Pacific Ocean [Fig. 1]. SSTs returned to near average in the eastern Pacific Ocean by the end of the month, as indicated by the latest weekly Niño-3 and Niño-1+2 index values of -0.3°C and -0.2°C, respectively [Fig. 2]. However, the latest weekly Niño index values in the central (Niño-4) and east-central (Niño-3.4) Pacific Ocean were -1.1°C and -0.7°C. The below-average SSTs were supported by negative subsurface temperature anomalies [Fig. 3], which extended from the surface to at least ~150m below the surface between 160°E and 130°W [Fig. 4]. Low-level wind anomalies remained easterly from the western to east-central (~140°W) tropical Pacific, with the largest amplitude near the Date Line. Upper-level wind anomalies were westerly across most of the tropical Pacific. Tropical convection continued to be suppressed over the western and central Pacific and enhanced around the Philippines and Indonesia [Fig. 5], while both the Southern Oscillation and Equatorial Southern Oscillation remained positive. Overall, the coupled ocean-atmosphere system remains consistent with La Niña.
Most of the models in the IRI/CPC plume predict a transition to ENSO-neutral during the Northern Hemisphere spring 2021 [Fig. 6]. The forecaster consensus is in agreement with this transition and then predicts a continuation of ENSO-neutral at least through the Northern Hemisphere summer. In part, due to the inherent uncertainty in predictions made at this time of year, the forecast for the fall remains split (~50%) between La Niña and the combination of the other two possibilities (El Niño and Neutral). In summary, there is a ~60% chance of a transition from La Niña to ENSO-Neutral during the Northern Hemisphere spring 2021 (April-June; click CPC/IRI consensus forecast for the chances in each 3-month period).
La Niña is anticipated to affect climate across the United States during the upcoming months. The 3-month seasonal temperature and precipitation outlooks will be updated on Thursday February 18th.