Fig. 1: The projected NOV/DEC/JAN 2022-23 ONI is -0.9C. Typically, the last La Nina-like ONI of a lengthy La Nina during NOV/DEC/JAN is followed by mixed ENSO results the following JUN/JUL/AUG all forecast as El Nino (by June) by leading models.
Discussion: La Nina 2020-23 is forecast to end during the first half of 2023. Typically, lengthy La Nina events with La Nina-like NOV/DEC/JAN to close the final year of the event are followed by a mixed result of the operational Nino index (ONI) the following JUN/JUL/AUG (Fig. 1). Of 8 lengthy La Nina regimes since 1950, two were followed by El Nino the following JUN/JUL/AUG while two maintained a weak La Nina and 4 events were neutral. Based on that observation, the climatological risk of ENSO phase for next JUN/JUL/AUG is 25% La Nina or El Nino and 50% neutral phase. Interestingly, all lead forecast models are projecting El Nino by June with Bureau of Meteorology/Australia strongest and NCEP CFS V2 weakest. The Climate Impact Company June Nino34 SSTA forecast is +0.2C although El Nino onset is forecast to follow in JUL/AUG.
If El Nino forms by boreal summer, the warm East Pacific equatorial zone will be accompanied by widespread anomalous warm SSTA in the subtropical/mid-latitude oceans (Fig. 2). The anomalous warm SSTA will add heat to the earth’s troposphere likely leading to a challenge of an all-time-record annual global warmth by year’s end.
Fig. 2: The North America multi-model ensemble (NMME) global SSTA forecast for JUN/JUL/AUG 2023.