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ENSO Alert System Status: La Niña Watch
Synopsis: ENSO-neutral is favored through the Northern Hemisphere summer and into the fall (51% chance for the August-October season), with La Niña potentially emerging during the September-November season and lasting through the 2021-22 winter (66% chance during November-January).
Near-average sea surface temperatures, consistent with ENSO-neutral conditions, were observed across most of the equatorial Pacific Ocean during June. In the last week, most Niño indices were near zero except for the Niño-1+2 index, which was +0.3oC. Subsurface temperature anomalies were slightly positive (averaged from 180-100oW) and remained steady during the month. However, in parts of the eastern Pacific, below-average subsurface temperature anomalies returned near the thermocline. For the month, the low-level and upper-level winds were near average across most of the equatorial Pacific Ocean. Tropical convection was suppressed near the Date Line, while remaining mostly near average elsewhere. Overall, the ocean and atmosphere system reflected ENSO-neutral conditions.
A majority of the models in the IRI/CPC plume predict ENSO-neutral to continue through the fall and winter 2021-22. However, the latest forecast model runs from the NCEPCFSv2, many of the models from the North American Multi-Model Ensemble, and some models from our international partners indicate the onset of La Niña during the Northern Hemisphere fall, continuing into winter 2021- 22. The forecaster consensus favors the semodel ensembles, while also noting the historical tendency for a second winter of La Niña to follow the first. In summary, ENSO-neutral is favored through the Northern Hemisphere summer and into the fall (51% chance for the August-October season), with La Niña potentially emerging during the September-November season and lasting through the 2021-22 winter (66% chance during November-January; click CPC/IRI consensus forecast for the chances in each 3-month period).