BOSTON (CBS) – If you love snow and winter storms, the current seven-day forecast is probably putting you to sleep. Not a flake or drop in the forecast in the Boston area, or most of New England, in sight.
I even received some tweets from people asking if this is it. Is winter over? Honestly, I don’t even know how to answer a question like that in early January. I think it has to be someone pulling my leg or someone who is not from New England – I mean, come on. We know better. Frankly, many made the same mistake in the beginning of mid-February earlier, calling to pierce a fork in the winter while Mother Nature is simply taking a brief nap. Frankly, until the Red Sox reaches the field in Fenway and the trees start to bloom, it’s never safe to count winter here. And yet, it is not a lock.
This winter was a little weird, but aren’t they all? Although no two winters are alike, we try to find the few large-scale factors at the beginning of each winter that can lead us in one direction or the other. This year, the main factor was (and still is) La Niña. A very strong La Niña, along with some other large-scale atmospheric tips, has led most meteorologists, including us at WBZ-TV, to call for a milder-than-average winter with less snow than average. And, of course, right away, we were hit by one of our biggest snowstorms in December ever recorded. Leaving the storm aside, things went well as planned. December averaged 1.3 degrees above average and so far January is more than 3 degrees warmer than average. Easy easy, right?
Well, not that fast.
This is where we present another one of those geeky weather terms, something that may be about to affect our winter forecast. I know you’ve all heard of Polar Vortex. But, have you heard of the grumpy neighbor upstairs in the 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 about 6 to 30 miles above the Earth’s surface. Although temperatures generally decrease with height in the troposphere, they do change and actually increase with height in the stratosphere. A “sudden stratospheric warming” is a rare event in which the winds in the stratosphere change from their typical direction from west to east, thus triggering a dramatic warming, often exceeding 50 degrees Celsius in just a few days! The effects this has on the climate around the world can be quite dramatic.
(WBZ-TV chart)
Essentially, this sudden heating causes a chain reaction in the atmosphere, starting from the top. In general, there is a strip of winds revolving around the Arctic, also known as the Polar Vortex. When these winds remain smooth and strong, they help to keep cold air bottled around the North Pole. A sudden stratospheric warming event (SSW) causes chaotic changes in the vortex, often forcing it to split into several different vortexes that tend to spread south in parts of Asia, Europe and North America.
(WBZ-TV chart)
Just as we say that no two winters are the same, we can also say that no two SSWs are the same. Take the past few years, for example. The SSW that took place in February 2018 turned a benign winter into a historic one. We had four blizzards in March, which fell nearly two inches of snow in Boston and caused massive coastal flooding and tree damage.
In contrast, SSW in January 2019 had opposite effects, leading to anomalous warming in parts of the United States and Europe.
So what effect will this year’s SSW have on Polar Vortex and our climate?
For the moment, the best we can say is stay tuned.
With the event still in its infancy, it is almost impossible to predict the wild ripples that are about to happen when dominoes fall from the Arctic southwards to our latitude. Initially, at least in the coming weeks, it appears that the most dramatic effects will occur in parts of Asia and northern Europe. The intense cold in response to the SSW is expected to plunge into these areas and you will likely hear news of record cold and snow from that side of the globe.
Typically, when these interruptions are at their worst, we can have a severe winter period of 30-45 days. For us, the deadline to be observed is clearly from the second half of January to mid-February. Could we go down to another historically cold and snowy stretch? Yes. But at this point, I would say that the odds also favor the worst impacts being on the other side of the globe, while our winter continues to be governed mainly by La Niña and more typical variations of the day-to-day.
Anyway, winter is far from over. Even in the mildest and most benign weather patterns, we can experience interruptions of cold and snow here and there. The above discussion is just a “warning” that great things are happening in the atmosphere right now. A giant bowling ball has been launched on the atmospheric track, whether our pins remain standing or not, has yet to be seen.
The WBZ-TV weather team will closely monitor developments in the coming days and keep you informed as the standard evolves. We plan to have a complete update to the winter forecast early in the week of January 18th, so stay tuned!
Follow Terry on Twitter @TerryWBZ