Highlight: BIG warm-up in the Pacific subsurface in April.
Discussion: Wow! Look at the warm-up in the subsurface equatorial Pacific Ocean (Fig. 1) during April! Amazingly, some borderline La Nina SSTA hang-on in the Nino regions (Fig. 2). ENSO is in neutral phase according to ENSO-expert Australia Bureau of Meteorology. The outlook indicates neutral phase for mid-year but confidence for the last 1/3 of 2021 is low…La Nina could return. Regardless, northern hemisphere climate patterns during the middle third of the year will largely be well-correlated to the mid-latitude SSTA patterns which are likely quite warm (Fig. 3).
Fig. 1: Equatorial Pacific Ocean subsurface temperature anomalies for the past 12 months are indicated.
Fig. 2: ENSO is in neutral phase (Nino34 SSTA is <-0.5). However, the far eastern equatorial East Pacific (Nino3/Nino12) are La Nina-cool.
Fig. 3: ECMWF global SSTA forecast for July 2021 projects very a very warm regime across the northern oceans.