Fig. 1: The 2020-22 La Nina episode as indicated by traditional Nino34 SSTA and multivariate ENSO index.
La Nina discussion: Based on the multivariate ENSO index (MEI), La Nina 2020-22 has reached a 3rd peak intensity at -1.5 for MAR/AUG 2022 (Fig. 1). Previous peak MEI were observed in June and October of 2021. The peak Nino34 SSTA index was also -1.5 during OCT/NOV 2020. MEI is an index identifying the atmospheric reaction to the equatorial Pacific SSTA/SLPA regime. Clearly, La Nina 2020-22 marches on and as ONLY indicted by NCEP CFS V2 from earlier this year will continue through the middle third of 2022 likely extending to early 2023. If La Nina lasts through quarter 1 of 2023 the event will reach 3 years in length the most since the 1998-2001 episode. The 1998-2001 La Nina was compensation of the ENSO System in response to the preceding 1997-98 El Nino which tied the 1982-83 El Nino episode for strongest on record. The 2020-22 La Nina did not follow a strong El Nino. In fact, based on MEI, 39 of the past 69 months have observed a La Nina climate.