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ENSO Tracker - May 2021 | CLIMAS

 SW Climate Outlook

ENSO Tracker - May 2021

ENSO Tracker - May 2021

Sea surface temperature (SST) forecasts for June – Aug 2021 call for normal conditions across the equatorial Pacific (Fig. 1). The current Nino 3.4/4 anomalies have returned to the range of neutral (Fig. 2), with further movement expected given the (warm) sub-surface waters. The ENSO outlooks note the end of the most recent La Niña event, with oceanic and atmospheric conditions decoupling and returning to normal (ENSO neutral).  

Forecast Roundup: On May 11, the Australian Bureau of Meteorology ENSO tracker was fully shifted to neutral/inactive, stating “ENSO is neutral with no indication that El Niño or La Niña will develop in the coming months.” On May 12, the Japanese Meteorological Agency (JMA) observed that La Niña “is coming close to its end”, with a 70-percent chance of neutral conditions over summer and autumn. On May 13, the NOAA Climate Prediction Center (CPC) ENSO status was the “Final La Niña Advisory”, and they called for a 67-percent chance of ENSO-neutral during June-August 2021. On May 19, the International Research Institute (IRI) issued an ENSO Quick Look (Fig. 3), noting ENSO-neutral SSTs and “the evolution of most key atmospheric variables are consistent with the end of La Niña conditions.”  The North American Multi-Model Ensemble (solid and dashed black line, Fig. 4) are back to ENSO-neutral, and are expected to remain neutral through summer.

Summary: La Niña conditions have ended, and ENSO neutral conditions have returned. The seasonal forecasts are bullish these will remain in the range of neutral through at least summer. Longer-term forecasts hint at the potential for a return of La Niña conditions in winter 2021/2022, but there is considerable uncertainty in these forecast. The picture (and the probability of a return of La Niña) should be clearer by the end of summer.

Online Resources

  • Figure 1 - Australian Bureau of Meteorology -
  • Figure 2 - NOAA - Climate Prediction Center -
  • Figure 3 - International Research Institute for Climate and Society -
  • Figure 4 - NOAA - Climate Prediction Center -