La Nina Continues to Weaken But Further Weakening Is Likely Temporary

Discussion: Oceanic La Nina continues to weaken. The Nino34 SSTA is just-within the La Nina threshold at -0.6C (Fig. 1). In the subsurface, the equatorial East Pacific is warming (Fig. 2) and east of the Dateline upper ocean heat is now warmer than normal (Fig. 3). However, southern oscillation index (SOI) remains in a robust positive phase implying stronger than normal trade winds across the equatorial East Pacific. The much warmer far West Pacific tropics compared with the slightly cool East Pacific tropics is a SSTA regime that will sustain La Nina climate despite the likely neutral phase of Nino34 SSTA ahead. Due to the likelihood of the La Nina persisting through Q3 of 2022, the Nino34 SSTA forecast by the NCEP CFS V2 model indicates short-term transition to neutral phase followed by La Nina returning (Fig. 4).

Fig. 1: The Nino34 SSTA is drifting toward neutral phase.

Fig. 2: Equatorial Pacific Ocean upper ocean heat anomalies indicate significant warming near the surface between 140W and 120W in the East Pacific.

Fig. 3: Upper oceanic heat is now warmer than normal in the equatorial Pacific Ocean to the east of the Dateline.

Fig. 4: Latest Nino34 SSTA forecast by the NCEP CFS V2 model.