The chance of an El Nino episode developing this year have greatly diminished as per the latest info from the IRI/CPC.

This has been a steadily building possibility which we’ve been examining at various points over the last number of months, with ENSO-neutral handily gaining ground as the favoured outcome.

Early August ENSO probabilities via the IRI:

figure1

The breakdown is now 72% La Nada / 16% La Nina / 12% El Nino for Sep-Oct-Nov 2017 and 56% La Nada / 28% La Nina / 16% El Nino for Dec-Jan-Feb 2017/18.

This is a marked change from even the previous mid-July info:

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Regardless, the trend has been firmly in this direction since we shook off the uncertainty of the spring forecast barrier.

This is their synopsis of current and expected conditions.

During July, ENSO-neutral continued, as equatorial sea surface temperatures (SSTs) were near average across most of the Pacific Ocean. The latest weekly Niño SST index values were close to zero in all four Niño regions, having recently decreased from higher levels in the Niño-4 and Niño-3.4 regions. The upper-ocean heat content anomaly was near average during July, reflecting below-average temperatures along the thermocline across the central and eastern Pacific overlain by slightly above-average temperatures. Tropical convection was near average over the eastern half of the Pacific and enhanced over the western Pacific and the Maritime Continent . The lower-level trade winds were slightly enhanced near the International Date Line, and upper-level winds were near average over most of the tropical Pacific. Overall, the ocean and atmosphere system remains consistent with ENSO-neutral.

The majority of models favor ENSO-neutral through the remainder of 2017. These predictions, along with the demise of the recent Pacific warmth and continued near-average atmospheric conditions over the Pacific, lead forecasters to favor ENSO-neutral through the winter. However, some chance for El Niño (15-20%) or La Niña (25-30%) remains during the winter. Also, ENSO-neutral conditions are predicted for the upcoming peak months (August-October) of the Atlantic hurricane season.

Nino 3.4 plume from the August run of the NMME:

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SST anomalies via the NMME:

NMME_ensemble_tmpsfc_season4

A look at SST anomalies as of August 10th:

anomnight.8.10.2017

This presents some added challenge to seasonal forecasts heading towards the winter months when ENSO typically exerts it’s greatest influence.

The last two ENSO-neutral winters were 2012-13 and 2013-14, both of which were governed by a variety of other factors such as anomalous ridging in the EPO and NAO domains. Early going to say if either of those years would be possible analogs at this juncture, along with any of the numerous other La Nada seasons from the past.

The big picture is gradually coming into focus as we go.

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