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Risk of record-setting 'Super' El Niño rising

Sea Surface Temperature (SST) anomalies for 28 June-4 July showing the warming central/east Pacific. Source: NOAA/ESRL/PSD

Sea Surface Temperature (SST) anomalies for 28 June-4 July showing the warming central/east Pacific. Source: NOAA/ESRL/PSD

Scott Sutherland
Meteorologist/Science Writer

Tuesday, July 14, 2015, 1:30 - Pacific typhoons may be setting up El Niño for a surge in strength, with the chances of it becoming the strongest on record rising.

As of the latest update from NOAA's Climate Prediction Center, this year's unusual El Niño pattern in the Pacific Ocean has an excellent chance of persisting through this year, and all the way until spring of 2016.

The current forecast shows at least a 90 per cent chance that El Niño conditions will last through winter 2015/16 - up to the end of February - and there is an over 80 per cent chance that it will still be active in April of next year. Also, it is already forecast to be a significant event, with sea surface temperatures likely reaching at least 1.5oC (2.7oF) above normal in the Central Pacific - the same intensity as the 1986/87 El Niño (which, coincidentally also matches the overall pattern of this year's El Niño development). However some models are still showing that it could grow stronger than that, possibly rivaling or even besting the 1997/98 "super" El Niño.

Computer model predictions for sea surface temperature anomaly (oC) for the central Pacific. Anything over +2.0 is considered a "super" El Niño. The 1997/98 event reached a maximum of +2.3. The overall forecast consensus is indicated by the thick black line. Credit: NOAA/CPC

What is feeding into the pattern to cause this surge? The powerful tropical storms and typhoons that have been developing in the western Pacific Ocean so far this year. This abundance of storms, which has been fueled by the strengthening El Niño, has overloaded the system with energy, as shown rather succinctly in this Tweeted graph by WSI Energy forecaster Todd Crawford:

The Western Pacific Ocean currently has nearly 9 times the normal amount of accumulated cyclone energy (ACE). The Central Pacific has more than 22 times the normal amount! Since ACE is a measure of the total time and intensity of storms that have formed in the region during the season, it's easy to see how much more active it is than normal. (Note: the Western Pacific bar is so much taller on the graph than the Central Pacific one because the bars are showing relative forecast vs climate average values. While the the climate average for the Western Pacific is already significant by this point, the average for the Central Pacific is near nil in early July. Therefore, even multiplying the ACE for the Central Pacific by 22.3 times only yields a very tiny bar.)

What, exactly, does all this ACE mean for El Niño?

According to the latest Australian Bureau of Meteorology ENSO forecast:

"The 2015 El Niño is likely to strengthen in the coming weeks, largely due to recent tropical cyclone activity. Several tropical cyclones, including a rare July cyclone in the southern hemisphere, have resulted in a strong reversal of trade winds near the equator. This is likely to increase temperatures below the surface of the tropical Pacific Ocean, which may in turn raise sea surface temperatures further in the coming months."

If this does happen, it would mean a strengthening for El Niño, but by how much is unknown.

What are the chances of a "super" El Niño now, with these latest developments? The consensus forecast (shown in the graph above) is likely correct, and this will simply turn out to be a significant or strong event, with fairly standard impacts on global weather patterns.

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However, as compared to the past two months of computer model runs, the ones above may have pulled back from the strongest predictions (those above +4.5oF), but the forecasts towards the weaker end have strengthened, and the overall consensus has gone up as well. NHC Hurricane Specialist Eric Blake shows, in the animated image he posted on Wednesday, how one just one of these models has increased its projections over the past month or so:

It takes more than just one of these models to produce a good forecast for El Niño, which is why the graph further up looks something like spaghetti being churned out of a pasta maker. Different computer models have different strengths and weaknesses, and the "consensus" results reflect the blending of results, to emphasize the strengths. However, it will be very interesting to see what the next batch of model runs produces, in the weeks to come.

At the same time, though, NOAA forecasters have been counseling calm and caution when it comes to checking out these short-term updates on the pattern of winds and temperatures in the Pacific Ocean.

First, the index used by NOAA to track the strength of El Niño, known as Oceanic Niño Index (ONI), is based on the average sea surface temperature anomalies over a three-month period. If ONI is 0.5oC (0.9oF) or higher, that is counted as an El Niño event, above 1.0oC (1.8oF) is a moderate event, above 1.5oC (2.7oF) is strong, and above 2.0oC (3.6oF) is very strong (or "super"). Weekly values in the model runs, however, can get lost in a three-month average. Thus, it's the longer-term look at the event that matters, not the short-term updates.

What, exactly, does this have to do with climate change?

Well, while El Niño and La Niña events are not expected to happen more often with climate change, when they do happen, climate change is expected to push them towards extreme levels. Furthermore, with the trend of soaring global temperatures from 2014 already pushing well into this year, we're already on the road towards breaking 2014's hold as the hottest year on record. Even a moderate El Niño could solidify 2015's place in the top spot on that list, but if El Niño 2015 matches the 1997/98 event, or surpasses it, this year may leave the past years far behind in the ranking.

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