It all started with a powerful Springtime Kelvin Wave. A trans-ocean telegraphing of heat that signaled the ramp-up toward El Nino during 2014. Heat spread out over the ocean surface and just beneath, but a failure of the atmosphere to respond to this forcing meant only the emergence of a weak El Nino by early 2015. At that time, it looked as if the El Nino could fade, adding to a long list of other weak-to-moderate events since the record-shattering years of 1997-1998.
But extraordinary westerly winds developed over the Western Pacific during late Winter and re-emerged through Spring. As a result, warm waters again gathered in an eastward surge across the Pacific — a Kelvin Wave more powerful than even the intense 2014 event.
(The Spring Kelvin Wave remains very hot into early June, showing some reinvigoration due to atmospheric feedbacks. Image source: NOAA’s Climate Prediction Center.)
By April and May it had flooded into a warm pool off the West Coast of South America, pushing surface waters into the peak values of 3-4 Celsius above average temperatures, while 5-6 C + above average temperatures lurked just below the surface.
By June, the Kelvin Wave had re-intensified even as it rebounded a bit off South America. Meanwhile, ocean surface heating continued to ramp up. By June 8, temperatures in the Central Pacific Nino 3.4 zone had hit a +1.2 C anomaly — already entering moderate El Nino range. Meanwhile, NOAA’s multivariate ENSO index showed that by June 4 the 2014-2015 El Nino was now stronger than any event since 1997-1998 with overall departures now exceeding the +1.5 C range. Such a departure marks a foray into strong El Nino territory:
(2014-2015 El Nino creeps into strong range exceeding all previous Equatorial Pacific warming events since 1997-1998. Image source: NOAA’s Earth Systems Research Lab.)
It’s important to note that models have very high uncertainty during the Spring due to a tendency of summer patterns to tamp down El Nino intensification. However, cloudiness has built and persisted over a broad band of the Equatorial Pacific — a factor spurring the most intense early season tropical cyclone development the Northern Hemisphere has ever seen. In addition, atmospheric wind patterns have continued to support El Nino strengthening. This continued pattern yesterday led WeatherUnderground blogger Bob Henson to this summation:
This time, the atmosphere and ocean are much more in sync, so we can put more trust in the current model outlooks—especially now that we’re past the “spring predictability barrier” that makes early-year forecasts of El Niño so tough. In today’s update, NOAA is calling for a greater than 90% chance that El Niño will continue through the northern fall of 2015, and around an 85% chance it will last through the winter of 2015-16.
Should El Nino start to peter out now, we’d be looking at something perhaps a bit stronger than the 2009-2010 event. But given the above trends, El Nino is still strengthening. A fact confirmed by forecast model runs that continue to show potential for a strong to potentially record-shattering event come Fall of 2015.
(Australian Bureau of Meteorology shows model runs predicting a strong to record shattering El Nino by October of 2015. Image source: BOM.)
All long range models now show Nino 3.4 sea surface temperatures predicted to hit between 1.5 and 3.0 C above base-line levels by October. Model averages now show a 2.4 C departure for all the major runs. Such an event would be extraordinary — equaling or exceeding the 1997-1998 El Nino (which topped off at 2.2 C above average in the three month measure).
All this information generates a clear picture of a still intensifying El Niño. One that has an increasing potential to develop into a real beast come Fall. As a result, we can expect continued global record hot temperatures to continue, as El Nino combines with an egregious human fossil fuel burning to shove global temperatures into ever-more-dangerous ranges. In addition, storm track intensification come Fall could be quite extreme when one considers both the possible strength of El Nino and the powerful atmospheric moisture loading due to a ramp up of temperatures into the range of +0.95 C above 1880s averages.
Hat Tip to Colorado Bob
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