Discussing a 2018 el-Nino

El Niño watch 2018

Roger Caldwell,via Facebook

Four days ago (9/26) a signature wind pattern appeared in the far west equatorial Pacific that greatly increases the probability of El Niño in the coming months. It doesn’t look like much — a small puff of gale force wind — but the location is what matters. Just east of the island of Papau New Guinea the waters are very vulnerable to surface wind, as it is these small puffs that mark the beginning of a climatic domino effect that can change the climate of nearly the entire earth, because it is here that the direction of the equatorial Pacific current begins its switch to an El Niño mode.

Equatorial waters are unique on earth because it is the only place which is not subject to coriolis forces which cause the direction of fluids to curve clockwise or counter clockwise depending of which side of the equator you are on. At the equator, fluids can flow straight for long distances, resulting in large translational movements of water. The Pacific Equator is by far the longest stretch of uninterrupted flow, exceeding 11,500 km.

Called a westerly “back burst”, the puff of gale force wind initiates a subsurface Rossby wave, which is a thermal wave that propagates along the equator from west toward the east. For the past several months the general direction of the surface wind has been anomalously westward, which has caused a build-up of subsurface heat across the central Pacific Equator. When this heat exceeds a +1C anomaly, it is a precondition for El Niño. Just before this latest back burst, the +1C threshold was crossed, and as a result, this back burst promises to push that anomaly significantly higher making an El Niño more intense.

For comparison, the 2015/16 El Niño peaked at an ocean heat content of +1.7C, with a peak subsurface intensity of +4C. Right now, we’re at a heat content of +1.1C, with a peak subsurface intensity of +3.5C and this is before accounting for the effects of the most recent back burst which has yet to be reported. (Date of subsurface heat graph 9/25/18).

What to expect.

It might take a couple more months for the equatorial surface water to switch from a “neutral” mode to a “warm” mode. Once switched, the intensity of the warm mode will depend heavily on whether or not we have more westerly back bursts. 

If no more back bursts happen, then we can expect a relatively mild El Niño; however, if back burst like this last one persists, then all bets are off as we could be headed toward a new record. 

The breadth of the subsurface anomaly is very large. Even though it is not as intense, it is wider than the 15/16 event, meaning that once it forms it could last longer. 

One thing for sure is that there is no cooling in sight.