NOVA MEDIA PUBLISHING INC.

75 % Chances La Niña Will Continue Through the Northern Hemisphere Winter

11.9.2020

In August, La Niña conditions were present, with below-average sea surface temperatures (SSTs) extending across the central and eastern equatorial Pacific Ocean (Fig. 1).  In the last week, all Niño indices were negative, with the Niño -3.4 index at -0.9ºC and the Niño-1+2 and Niño-3 indices were cooler than -1.0ºC.  Equatorial subsurface temperature anomalies averaged across 180°-100°W and were negative, with the largest departures observed in the east-central Pacific from the surface to 200m depth.   

Atmospheric circulation anomalies over the tropical Pacific were also generally consistent with La Niña, despite sub-seasonal variability during the month.  The low-level and upper-level winds were near average for the month, but enhanced low-level easterly winds were prominent across the equatorial Pacific Ocean during early and late August. 

Tropical convection remained suppressed over the western and central Pacific and was near average over Indonesia.  Both the Southern Oscillation and Equatorial Southern Oscillation indices were positive.  Overall, the coupled ocean-atmosphere system was consistent with La Niña conditions.   

Most of the models in the IRI/CPC plume predict the continuation of La Niña (Niño-3.4 index less than -0.5°C) through the Northern Hemisphere winter 2020-21.  The forecaster consensus supports that view and favors a borderline moderate event (Niño-3.4 index near -1.0ºC) during the peak November-January season.  In summary, La Niña conditions are present and are likely to continue through the Northern Hemisphere winter (~75% chance). 

Colder temperatures and drought are expected in the Pacific side in Ecuador and Peru and higher temperatures and abundant rains in the banana producing countries in the Atlantic and the Caribbean. 

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