Using Multivariate ENSO Index, The 2023-24 El Nino Was Very Weak

Fig. 1: Multivariate ENSO index sequence for each El Nino episode since 1979.

Discussion: Multivariate ENSO index (MEI) is an index used to identify the atmospheric response of the sea surface temperature (and pressure) anomalies in the Pacific equatorial region. The 2023-24 El Nino episode, according to MEI, was the 3^rd weakest (MEI = 0.68) since 1979 despite moderate to strong oceanic intensity using conventional Nino34 index. Speculated are the record warm global oceans of APR-23 to JAN-24 contributed to the weaker El Nino climate pattern. Since 1979, the weakest El Nino events using MEI were observed in 1979-80 (MEI = 0.53) and 2006-07 (MEI = 0.61). The strongest El Nino events since 1979 occurred in 1997-98 (MEI = 2.07) and 1982-83 (MEI = 2.01). The MEI average for the 12 events considered is MEI = 1.11.