Super Strong El Nino – End Game underway

The Strong El Nino of 2016, one of the strongest in recent times, that sparked record temperatures across the globe, is gradually on the decline across the equatorial Pacific Ocean and transition to neutral state is likely by the end of spring season.

El Nino is defined as above-average sea surface temperatures across the equatorial central and eastern Pacific Ocean. These sea surface temperatures cycle from warm state to cool phase over a period of time. The current 2015-16 El Nino event was strongest El Nino on record in terms of record temperatures across the globe. Much of the tropics experienced above-average temperatures in winter and also are experiencing early summer with temperatures remaining quite high at this time of the year.

However, in the grand scheme El Nino has been gradually fading since January. The heat flux in the Nino region has declined following December, and the cool anomalies from west-central Pacific has propagated eastwards since February indicating the decaying process of El Nino.

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As one can observe from this model, the negative anomalies/cool sub-surface waters (blue color), were observed in west-central Pacific in January, which has propagated eastwards over the last month under the influence of upwelling of oceanic Kelvin wave.

The upwelling of oceanic Kelvin wave clearly emerged across the western Pacific from January 2016 and gradually propagated east-ward over the last month, resulting in the increasing thermocline across the central-eastern Pacific. Another factor which shows the easing of warm waters has been the heat flux that has been in negative state since December 2015 as shown in below graph.

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Heat flux can be definied as the amount of heat that passes through a surface, and it arises due to temperature differences.

Also, during much of the last couple of months, the trade winds have clearly shown signs of strengthening and currently are back to near normal across the region. The Pacific Ocean current are also in full force moving in west-ward direction, thus pushing all the warm waters to the west. Hence it would be a matter of time before we start talking the 2015 – ’16 ElNino in  historical context.

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The atmospheric component of ENSO “Southern Oscillation Index” also continue to support the idea of fading El Nino with increasing values over the 30-day average as shown in the table below.  When SOI consistently stays above -8 then we could confirm the El Nino episode is over and we have moved into neutral phase of ENSO

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Although the strong El Nino is fading across the Pacific Ocean, its influence in atmospheric pattern will continue to persist for at least next couple of months. Since Ocean stores large amount of heat, the fading El Nino will release heat that is stored into the atmosphere and the atmosphere responds by raising the temperatures across the tropics.

However, the question is whether we will see La Nina in the second half of 2016. While numerical weather models are uncertain in current scenario, the chances of La Nina to develop by summer/fall looks good with already signs of increased convection across NW Australia and also the wet-pattern returning to Indonesia.