La Nina May Fade But Atmosphere Stays Locked-in on La Nina Climate

Discussion: The mid-latitude oceanic regime influence on global climate patterns has increased dramatically during the past decade. However, ENSO certainly reigns as the leading contributor. The mid-latitude SSTA regime has rendered the ENSO pattern(s) different from years past and more difficult to predict.

Right now, the 2020-22 La Nina has regained strength. The equatorial Pacific has cooled sharply in recent weeks after a marginal La Nina presence during much of quarter 1 of 2022. The southern oscillation index (SOI) is the most La Nina-like monthly signature of the entire 2020-22 La Nina episode at a whopping +2.00 (Fig. 1). The multivariate ENSO index (MEI) strengthened from -1.0 in JAN/FEB to -1.3 in FEB/MAR and is likely to maintain that strong La Nina climate signature when the MAR/APR index is released later this week.

So, the atmospheric La Nina is firm! A leading predictor of where ENSO phase is going is (generally) the subsurface equatorial upper ocean heat trend. The April 2022 observations reveal that on average subsurface waters are slightly cool and have warmed slightly since March and are nowhere near the cool support present late last year (Fig. 2). The subsurface upper ocean trend indicates ENSO phase ahead is likely to turn neutral.

In summary, ENSO will have a significant influence on the middle third of 2022 global climate. Despite the oceanic definition of ENSO phase shifting to neutral, the global climate pattern is likely to stay in La Nina mode. All climate forecasts for the middle third of 2022 should be biased toward La Nina influence.

Fig. 1-2: Southern oscillation index for each month of the 2020-22 La Nina episode and equatorial Pacific upper ocean for the past 12 months.