95% chance the strong El Nino–among the strongest on record–continues into next year–but its impact on this winter’s weather isn’t nearly as certain
by TOM SKILLING Today at 12PM
The common wisdom is that strong El Ninos make for milder than normal and less snowy winters across the northern Plains into the Midwest. But this not always true. The fact is, not all El Ninos are created equal. There’s little doubt the current record strong El Nino–the warming of the equatorial Pacific Ocean from South America to the dateline (as depicted in the global ocean temp anomaly graphic out of NOAA and the University of Maine which appears at the top of this post) above–will continue through the coming winter and into 2016. The probability of that taking place is put at 95% by NOAA climate forecasters. And it’s also been widely reported and accepted that this El Nino ranks in the top tier of such events.
The official Climate Prediction Center Dec through Jan outlook follows long observed relationships between strong El Ninos and cold season weather trends, indicating above normal temps and below normal precipitation from the northern Plains into the Midwest in the December through February period. But this forecast should be qualified and used with care. The prediction isn’t carved in stone–it’s a best guess based on the information currently at hand. Many of you write for thoughts on what the coming winter may hold for us and there are a series of unsettled questions in my mind about factors which might intercede and throw the usual El Nino-winter weather relationship here and elsewhere off the usual track. This winter could for a number of reasons follow the lead of the past several winters and end up near or below normal. It would have to work at doing so. Bucking a strong El Nino isn’t impossible–but it’s not an easy thing for nature to do either.
We live on a planet in the midst of climate change. It’s oceans are exhibiting even more rapid warming than the atmosphere. The energy which has accumulated in the world’s oceans since 1990 has been likened to the energy which would have been released had a Hiroshima strength atomic bomb had been ignited every second over that period of time. Check out the extent of warmer than normal water in the Pacific Ocean and Gulf of Alaska. Not all of this is El Nino inspired. And the warm ocean waters in the eastern North Pacific and in the Gulf of Alaska (off western North America) have, arguably, had a profound affect on recent winters. Air over the warm ocean waters also warms, and this appears at least one factor in the build-up of a ridge over western North America which has contributed to the diversion of needed precipitation away from the western U.S. while contributing to the ridging (i.e. northward “buckling”) of the jet stream which has kept us cold in recent winters with huge Great Lakes ice buildup. It wouldn’t be hard to imagine some version of this happening again this winter–and that would profoundly change the current “warmer than normal” winter season forecast.
Snowfall is always the more difficult parameter to predict. But were there to be a colder winter than currently forecast, the effect would be to increase snowfall downwind from the Great Lakes. And, while it may or may not prove relevant, we looked a snow seasons which followed warm Septembers—-i.e. Septembers which finished with temps more than 4-deg above normal, as just-completed Sept 2015 did. We found six such snow seasons—and four of the six finished with above normal snow tallies. Such an outcome would be the opposite of what one might expect in a strong El Nino cold season.
A post by Deke Arndt of the National Center for Environmental Information (formerly NOAA’s National Climatic Data Center) on NOAA’s Climate.com website, does a nice job of stressing the notion that all El Ninos are NOT created equal and that believing they are is folly. It’s a theme which has been sounded by a series of scientists who post on NOAA’s ENSO blog—and it has real world implications as we look ahead to the weather of the coming months. Check Deke Arndt’s blog post out here.
And, while the large scale trends are consistent among seasonal forecast models, you’ll note subtle changes in the placement of cold and warm air pools in these projections into the coming December through January cold season.
One thing which is quite clearly indicated in this plot of average global temps, El Nino years (displayed on this graph in red) are warmer than their counterparts. Also clear is the steady increase in global temps over the term of this plot and the manner in which El Ninos have “boosted” or accelerated the trend toward rising temps when they’ve occurred. at 10.58.01 AM Here are depictions of the kind of ocean temp distributions which occur in an El Nino versus a La Nina.
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