NOVA MEDIA PUBLISHING INC.

90% Chance for La Niña to Continue Through the Northern Hemisphere Winter 2021-22

12.11.2021

According to the National Oceanic and Atmospheric Administration (NOAA) of the USA, La Niña strengthened in the last month, with below-average sea surface temperatures (SSTs) evident across most of the equatorial Pacific (Fig. 1).  In the last week, all the Niño index values were between -0.7ºC and -1.0ºC, with the coolest anomalies in the Niño-3.4 region.  Below-average subsurface temperatures (averaged from 180-100ºW) were roughly the same amplitude at this time last month, and reflected the prevalence of below-average temperatures in the eastern Pacific Ocean.  Low-level easterly and upper-level westerly wind anomalies were again observed over parts of the equatorial Pacific, although weaker than last month.  Tropical convection was suppressed near and west of the Date Line and was slightly enhanced over Indonesia. 

The Southern Oscillation Index and Equatorial Southern Oscillation Index remained positive. Overall, the coupled ocean-atmosphere system was consistent with La Niña. 

The IRI/CPC plume average of forecasts for the Niño-3.4 SST index favors La Niña to continue through January-March 2022 season.  The forecaster consensus predicts La Niña to persist longer, potentially returning to ENSO-neutral during April-June 2022.  The Niño-3.4 index has a 66% chance of reaching a value less than -1.0ºC during November 2021 – January 2022, but only a 14% chance of being below -1.5ºC.  Thus, at its peak, a moderate-strength La Niña is favored. 

In summary, La Niña is likely to continue through the Northern Hemisphere winter 2021-22 (~90% chance) and into spring 2022 (~50% chance during March-May). 

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