Models Signal La Nina's Arrival This Fall

Posted on 03/09/2017 10:21 AM

ENSO-neutral conditions lingered over the past month, states the National Oceanic and Atmospheric Administration (NOAA), featuring slightly below-average sea surface temperatures (SSTs) close to the equator across the eastern tropical Pacific Ocean. Atmospheric anomalies over the tropical Pacific Ocean also indicated ENSO-neutral conditions.

enso_aug112016""Both the traditional Southern Oscillation index and the equatorial Southern Oscillation index were near average during July, while the upper and lower-level winds also were near average across most of the tropical Pacific," states NOAA. "Convection was suppressed over portions of the western and central tropical Pacific and enhanced over part of Indonesia. Overall, the combined ocean and atmosphere system is reflective of ENSO-neutral."

ensoprobabilities_aug2016NOAA says many models favor La Niña at the beginning of the Northern Hemisphere fall and continuing into winter. "Statistical models predict a slightly later onset time (i.e., mid- to late fall) than dynamical models, and also predict a slightly weaker event," states the agency. "The forecaster consensus favors La Niña onset during the August-October season, and predicts a weak event (Niño-3.4 index between -0.5°C and -1.0°C) if La Niña forms. Overall, La Niña is slightly favored to develop during August-October 2016, with about a 55-60% chance of La Niña during the fall and winter 2016-17."


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