El Nino Ahead but Marine Heat Wave Needs to Strike West Coast of North America for Stronger El Nino in 2023

Executive summary: Strong conflicting signals are presented within the ENSO System during the mid-point of the ENSO seasonal prediction barrier. The Nino12 SSTA region off the northwest coast of South America has warmed rapidly and impressively as daily SSTA in this region is approaching a whopping +3.0! However, despite the super warming, the Nino34 SSTA region covering the east-central equatorial Pacific where ENSO phase is monitored is a resilient neutral phase with daily SSTA observations stuck near zero. In the Northeast Pacific, a large area of cooler than normal water is shifting southwestward via the California Ocean Current toward the central and east-central tropical Pacific maintaining the near neutral SSTA signature. Marine heat wave (MHW) NEP22A has shifted well to the west (north and northwest of Hawaii) and has allowed the Northeast Pacific to cool the past several months. NEP22A is forecast to stay off the West Coast despite some eastward shifting mid-to-late 2023. Consequently, the cool surge of water from northern latitude into the tropics is likely maintained through the middle third of 2023 preventing significant warming of the Nino34 SSTA region. Finally, multivariate ENSO index (MEI) remains consistent with a La Nina climate despite the ending of oceanic La Nina last month. The La Nina climate fades over the next 1-3 months but delays onset of a weak El Nino until mid-year with warm ENSO intensity for the remainder of 2023 still in-doubt although favoring weak-to-moderate intensity. El Nino is expected to continue in 2024 although intensity remains uncertain. A stronger El Nino is reliant on the MHW north and northwest of Hawaii shifting east and reaching the West Coast of North America with intensity. If so, a vigorous El Nino regime develops. However, while global SSTA forecasts are forecasting a vigorous El Nino in 2023, the complementary very warm Coastal Northeast Pacific required to cause strong El Nino is not expected.

Fig. 1: The Climate Impact Company Nino34 SSTA forecast to determine ENSO phase through 2024. Weak El Nino in 2023 persists in 2024.

Fig. 2-3: The Nino12 SSTA off the South America northwestern coast is prohibitively warm while the Nino34 SSTA region in the east-central equatorial Pacific is exactly neutral ENSO.

Fig. 4-5: Daily Northeast Pacific SSTA analysis reveals the marine heat wave westward shift and the resulting cooling off the North America West Coast. Cool waters are moving southwestward via the California Current toward the tropics.

Fig. 6: Multivariate ENSO index identifies the global climate reaction to the equatorial Pacific SSTA environment. The MEI reveals a global La Nina climate persists although weakening while oceanic La Nina ended last month.

Fig. 7: Dynamic global SSTA forecasts including ECMWF are aggressively forecasting a strong El Nino by August 2023. However, these aggressive El Nino forecasts are generated at a time of year when ENSO phase change is very difficult to predict. Climate Impact Company indicates the MHW north of Hawaii needs to shift east and reach the West Coast of North America for the aggressive El Nino to develop as observed during the 2015-16 episode.

Fig. 8: The Climate Impact Company ENSO phase probability forecast yields an El Nino solution with increasing risk of a stronger El Nino later this year.