BOSTON (CBS) – If you’re a fan of snow and winter storms, your current seven-day forecast will probably put you to sleep. No flake or decrease in the forecast in the Boston area, or in most of New England, in sight.
I even received a few Tweets from people asking if it was. Is winter over? Honestly, I don’t even know how to answer such a question in early January. I think it must be someone who’s kicking my leg, or someone who’s not from New England – I mean, come on. We know better. Honestly, many made the same mistake in early to mid-February before, calling for a fork to stick in the winter, while Mother Nature simply takes a short nap. Honestly, until the Red Wives hit the Fenway field and the trees start to bloom, it’s never safe to count winter here. And even then, it’s not a lock.
This winter was a little weird, but isn’t it all? Although there are never two similar winters, we try to find a few large-scale factors at the beginning of each winter that can lead us in one direction or another. This year, the main factor was (and still is) La Nina. A fairly strong La Nina, along with a few other large-scale weather suggestions, prompted most meteorologists, including us at WBZ-TV, to call for a milder-than-average winter with less-than-average snowfall. And, of course, right off the bat, we were hit by one of the biggest snowstorms in December. Aside from that storm, things went pretty much as planned. December was on average 1.3 degrees above average and so far January is over 3 degrees warmer than average. Easy to fill, right?
Well, not so fast.
Here’s where we introduce another of those weird weather terms, something that might be about to throw a key in our winter forecast. I know you’ve all heard of the Polar Vortex. But, you heard about the grumpy neighbor of the upstairs Vortex, Sudden stratospheric heating? Well, let me introduce you.
(WBZ-TV chart)
First, the stratosphere is the layer of air above the troposphere (where we live) that extends from about 6 miles to 30 miles above the Earth’s surface. While temperatures generally drop with height in the troposphere, they turn upside down and actually increase with height in the stratosphere. A “sudden stratospheric warming” is a rare event in which the winds in the stratosphere move from their typical west-east direction, triggering a dramatic warming, often exceeding 50 degrees Celsius in just a few days! The effects this has on the weather around the world can be quite dramatic.
(WBZ-TV chart)
In essence, this sudden warming causes a chain reaction in the atmosphere, starting from the top. Generally, there is a ribbon of winds that revolves around the Arctic, also known as the Polar Vortex. When these winds remain tight and strong, they help keep the cold bottled air around the North Pole. A sudden stratospheric warming (SSW) event causes chaotic vortex changes, often forcing it to split into several different vortices that tend to spill south into parts of Asia, Europe and North America.
(WBZ-TV chart)
Just as we say that no two winters are alike, we can say that no two SSWs are alike. Take, for example, the last few years. The SSW that took place in February 2018 turned an otherwise benign winter into a historic one. We had four nor’easters in March, which fell almost 2 meters of snow in Boston and caused massive coastal flooding and damage to trees.
Instead, SSW in January 2019 had very opposite effects, leading to abnormal heat in parts of the US and Europe.
So what effect will this year’s SSW have on Polar Vortex and our weather?
At this point, the best thing we can say is to be careful.
With the event still in its infancy, it is almost impossible to predict the wild ripples that will occur as dominoes fall from the southern Arctic to our latitude. Initially, at least for the next few weeks, it seems that the most dramatic effects will be in parts of Asia and northern Europe. The severe cold in response to the SSW is expected to sink into those areas, and you’ll probably hear reports of record cold and snow on that part of the globe.
Usually, when these interruptions are the worst, we can get a period of 30-45 days of harsh winter weather. For us, the deadline is clearly the second half of January to mid-February. Could we descend into another cold, snowy historical expanse? Yes. But at this point, I would say that the odds also favor the worst effects on the other side of the globe, while our winter continues to be governed mainly by La Nina and more typical daily variations.
Either way, winter is far from over. Even in the mildest and most benign weather patterns, we are forced to receive interruptions of cold and snow here and there. The above discussion is just a “head up” that big things are happening atmospherically right now. A giant bowling ball was thrown on the atmospheric strip, whether our people remain standing or not, remains to be seen.
The WBZ-TV weather team will closely monitor developments in the coming days and keep you up to date with the evolution of the pattern. We plan to have a complete winter forecast update at the beginning of the week of January 18th, so stay tuned!
Follow Terry on Twitter @TerryWBZ