BOSTON (CBS): If you’re a lover of snow and winter storms, the current seven-day forecast is likely to put you to sleep. Not a flake or a drop in the forecast in the Boston area, or in most of New England, in sight.
I’ve even received a few tweets from people asking me if that’s it. Is winter over? Honestly, I don’t even know how to answer such a question in early January. I guess it must be someone pulling my leg or someone who isn’t from New England, I mean. We know it better. Frankly, many have made the same mistake in early to mid-February before, calling for a fork in the winter, while Mother Nature simply takes a brief nap. Frankly, until the Red Sox reach Fenway Field and the trees start to bloom, it’s never safe to count winter here. And yet, it’s not a lock.
This winter has been a little weird, but aren’t they all? While no two winters are ever the same, we try to find the few large-scale factors at the beginning of each winter that can steer us in one direction or another. This year, the main factor was (and still is) La Nina. A fairly strong La Nina, along with some other large-scale atmospheric suggestions, caused most meteorologists, including us at WBZ-TV, to call for a milder-than-average winter with less snow than average. And of course, one of our biggest snowstorms of December hit us right away. Aside from this storm, things have gone pretty much as planned. December had an average of 1.3 degrees above average, and so far January is more than 3 degrees warmer than average. Easy, right?
Well, not so fast.
This is where we introduce another of these geeky weather terms, which may be about to throw a wrench into our winter forecasts. I know you’ve all heard of the Polar Vortex. But, you’ve heard of the thick neighbor upstairs in the Vortex, Sudden stratospheric warming? Well, let me introduce you.
(WBZ-TV chart)
First, the stratosphere is the layer of air that exists over the troposphere (where we live) that extends from about 6 miles to 30 miles above the earth’s surface. Although temperatures generally decrease with height in the troposphere, they rotate and in fact increase with height in the stratosphere. A “sudden stratospheric warming” is a rare event in which stratosphere winds change from their typical westerly direction to the east, causing spectacular warming, often exceeding 50 degrees Celsius in a few days. The effects this has on the climate around the world can be quite dramatic.
(WBZ-TV chart)
Basically, this sudden warming causes a chain reaction in the atmosphere, which starts from above. In general, there is a wind band that revolves around the Arctic, also known as the Polar Vortex. When these winds stay strong and strong, they help keep cold air bottled around the North Pole. A sudden stratospheric warming (SSO) causes chaotic changes in the vortex, which often forces it to split into multiple different vortices that tend to spill southward into 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. Just take the last few years for example. The SSW that occurred in February 2018 turned a benign winter into a story. In March we had four northeasters who fell nearly 2 feet of snow in Boston and caused massive flooding on the coast and damage to trees.
In contrast, SSW in January 2019 had very opposite effects, causing abnormal heat in parts of the United States and Europe.
So what effect will this year’s SSW have on the Polar Vortex and our climate?
Right now the best we can say is to be vigilant.
With the event still in its infancy, it is almost impossible to predict the wild ripples that are about to occur as dominoes fall from the Arctic south to our latitude. Initially, at least over the next few weeks, it looks like the most dramatic effects will occur in parts of Asia and northern Europe. The intense cold in response to the SSW is expected to submerge in these areas and you are likely to hear reports of record cold and snow news from that side of the world.
Normally, when these alterations are worse, we can get a hard winter period of 30 to 45 days. For us, the calendar to see is clearly from the second half of January to mid-February. Could we go down to another historically cold, snowy stretch? Yes. But at this point, I would say that the odds equally favor the worst impacts on the other side of the planet, while our winter continues to be ruled primarily by La Nina and by more typical day-to-day variations.
Either way, winter is far from over. Even in the mildest and most benign weather patterns, we are bound to suffer interruptions of cold and snow here and there. The above discussion is nothing more than an “upside down” than the big things happening atmospherically right now. A giant bowling ball has been thrown down the atmospheric lane, whether our needles remain standing or not, remains to be seen.
The WBZ-TV weather team will keep a close eye on the evolution of the coming days and will keep you informed as the pattern evolves. We plan to have a full winter forecast update early in the week of January 18th, so stay tuned.
Follow Terry on Twitter @TerryWBZ