Well, it’s official. According to NOAA’s May 14 update, we are now looking at a 90 percent chance that El Nino conditions prevail through Northern Hemisphere Summer and a greater than 80 percent chance El Nino will last throughout all of 2015:
(Climate Prediction Center’s ENSO probability forecast shows 90 percent chance of El Nino through June, July and August and a greater than 80 percent chance that El Nino continues on through to the end of this year. Image source: CPC/IRI.)
What this means, especially when we add in likely record warm global atmospheric temperatures (due to an excessive burning of fossil fuels by human beings) throughout the El Nino event period, is some rather odd, and probably extreme summer weather.
For the US, it means an increasing likelihood of heavy precipitation events from the southern plains states through the desert southwest. Storm track intensification through the Pacific to North America means that extreme rainfall events are a distinct possibility for states like Texas, Oklahoma, Colorado, Arizona, Nevada, and New Mexico. California may even see some abnormal summer rainfall, taking a bit of the edge off the current drought.
Moving southward, we find drier conditions for equatorial South America and warmer than normal conditions for much of Brazil and Chile. Northern Hemisphere Summer El Nino also enhances the risk of drought throughout Australia, Southeast Asia, and India. In particular, India is vulnerable to monsoonal disruption due to emergence of El Nino during summer time. Enhanced precipitation near the date line also can spur increased cyclone development for the Western Pacific.
(A geographic representation of major prevailing summer El Nino teleconnections. Image source: Berkley.)
These sets of atmospheric changes are what we could generally expect from a typical El Nino emerging throughout Northern Hemisphere summer. But we’re not really dealing with normal conditions. We’re dealing with global temperatures in the range of +0.8 degrees C above 20th Century averages and + 1 C above 1880s averages. As such, we should probably look to the margins for potential added impact.
Two areas in particular come to mind when considering such outliers. The first region is a zone from Ukraine through to Western Russia. Under added human heat forcing and conditions prevalent during summer El Ninos, this region shows an increased likelihood of drought and heatwave. A vulnerability that became particularly apparent during the El Nino of 2009-2010. Drought conditions are somewhat widespread for that region already this year. In addition, atmospheric high pressure development in this vulnerable area would now, with the enhanced surface warming due to human heat forcing, telegraph into the Arctic through a vulnerable zone near Yamal and the Kara and Laptev Seas. This would particularly enhance snow melt, permafrost thaw, and sea ice melt throughout this region. So with El Nino now a summertime certainty, this broader area certainly bears watching.
(El Nino teleconnection to warming in Northwestern North America through to the Arctic Ocean and in regions of Central, Western and Northern Asia are possible this summer. Above is a GFS model forecast temperature anomaly summary provided by The University of Maine’s Climate Reanalyzer.)
The second region to look out for is the zone ranging from Northwest Canada through Alaska and on into the Chukchi and Beaufort Seas. Summer El Ninos tend to enhance warming for this region. When adding in an already persistent heating throughout 2015 winter and spring, the area will fall under greatly heightened risk of severe wildfires and extreme and early snow and sea ice melt. Early extreme wildfires in British Columbia combined with rapid sea ice recession already ongoing through the Beaufort and Chukchi may well be indications that such a trend has already asserted.
Some Long Range Models Are Still Freaking Out Over a Potential Monster El Nino Later This Year
Moving beyond summer, we find a wide range of model consensus estimates showing strong El Nino by fall and winter of this year. NINO 3.4 departures from an average of global model ensembles compiled by Weather Underground hit a value of +1.7 C by September. A level just below the so-called Super El Nino Threshold of +1.8 C.
NOAA CFSv2 ensembles have continued to ramp higher. Weighted seasonal means have now spiked to +2.75 C for the key NINO 3.4 region with unweighted ensembles hitting +3 C for October, November and December. Weighted monthly means have spiked to +3 C anomaly for November while unweighted anomaly values for the same month have proceeded off the charts to an implied +3.5 C:
(Some El Nino forecast models, like the one above, are really freaking out about the potential for a monster event by the end of this year. This NOAA model is basically off the charts. Image source: NOAA’s Climate Prediction Center.)
Should these predicted values emerge, they will literally blow the 1998-1999 Super El Nino out of the water. A monster event to shatter all records.
It’s likely that the currently extreme subsurface temperatures due to a very strong warm Kelvin Wave as well as continued powerful west wind back-bursts have kicked these models into freak out mode. And it’s certainly an issue worth keeping an eye on.
But it’s also worthwhile to consider that global deep ocean and atmospheric dynamics will push to cool equatorial Pacific waters during September, which would tend to tamp down warming extremes. A factor that many models, which measure the shallow water zone primarily, tend to miss.
Dr. Kevin Treberth, a top expert on El Nino and Ocean Temperature dynamics, notes to Weather Underground in a recent interview that:
“What happens after this Kelvin wave response is all over the place. This El Niño is being fought by the annual cycle, which tries to make SSTs cold by Sept-Oct. That tendency keeps the warmest waters back near the International Date Line and cuts off the Bjerknes feedback. If the SSTs develop to be big enough to overcome the annual cycle tendencies, then the Bjerknes feedback can kick in.”
For reference, Bjerknes feedback involves storm formation and subsequent west wind backbursts east of the Date Line and on toward South America. A feedback that tends to trap and channel ocean surface heat into the relevant El Nino zones and generally enhance warm sea surface temperature anomalies:
(Graphic illustration of Bjerknes feedback showing sea surface temperature anomalies in the color measure and direction of wind flow indicated by black lines. It’s feature influenced by a general shoving of the Walker Cell eastward [implied but not shown]. Image source: ENSO as an Integrating Concept of Earth Science.)
So, at this point, we have a lock on a weak to moderate El Nino event continuing through this summer. After that time, an unprecedentedly warm Kelvin Wave will do battle with a seasonal tendency for cooling in the Eastern Equatorial Pacific. And if it wins out, we may see something never before recorded in the whole of the Earth Sciences — which would be very bad news for rates of global surface temperature increase this year, along with a huge number of other issues.
If not, we likely have a mid ocean El Nino through Fall and Autumn. And that may be bad news for a California desperately in need of drought relief.