BOSTON (CBS) – If you’re a fan of snow and winter storms, the current seven-day forecast will likely put you to sleep. Not a flake or drop in the weather forecast in the Boston area, or most of New England for that matter, in sight.
I even got a few tweets from people asking if this was it. Is the winter over? To be honest, I don’t even know how to respond to such a question in early January. I think it must be someone pulling my leg or someone not from New England – I mean, come on. We know better. In all fairness, many have made the same mistake in early to mid-February, sticking a fork in the winter while Mother Nature simply has a short siesta. Honestly, until the Red Sox hit the field at Fenway and the trees start to bloom, it’s never safe to count the winter here. And even then it is not a lock.
This winter was a bit strange, but aren’t they all? While no two winters are the same, at the beginning of each winter we try to find the few large-scale factors that can steer us in one direction or another. This year, La Nina was (and still is) the most important factor. A pretty strong La Nina, along with a few other large-scale atmospheric hints, led most meteorologists, including us at WBZ-TV, to demand a milder-than-average winter with less snow than average. And of course we were immediately hit by one of our biggest December snow storms ever. Aside from that storm, things have pretty much gone according to plan. December averaged 1.3 degrees above average and so far January is more than 3 degrees warmer than average. Easy-peasy right?
Well, not that fast.
Here we introduce another of those geeky weather terms, something that might be about to throw a wrench into our winter forecast. I know you have all heard of the Polar Vortex. But did you hear from the grumpy upstairs neighbor of the Vortex, Sudden stratospheric warming? Well, let me introduce you.
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First, the stratosphere is the layer of air above the troposphere (where we live) that stretches from about 6 miles to 30 miles above the Earth’s surface. While temperatures generally decrease with height in the troposphere, they flip and even increase with height in the stratosphere. A “sudden stratospheric warming” is a non-rare occurrence where the winds in the stratosphere switch from their typical westerly direction to an easterly direction, causing dramatic warming, often over 50 degrees Celsius in just a few days! The effects this has on weather around the world can be quite dramatic.
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In essence, this sudden warming causes a chain reaction in the atmosphere, starting from above. In general, there exists a ribbon of winds swirling around the North Pole, also known as the Polar Vortex. When these winds remain tight and strong, they help hold up the cold air around the North Pole. Sudden stratospheric warming (SSW) causes chaotic changes in the vortex, often splitting it into several different eddies that tend to flow south to parts of Asia, Europe, and North America.
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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 years, for example. The SSW that took place in February 2018 turned an otherwise benign winter into a historic one. We had four nor’easters in the month of March dropping nearly two feet of snow in Boston, causing massive coastal flooding and tree damage.
In contrast, the SSW had many opposite effects in January 2019, leading to abnormal heat in parts of the US and Europe.
So what effect will this year’s SSW have on the Polar Vortex and our weather?
Right now, the best we can say is stay tuned.
Now that the event is in its infancy, it is nearly impossible to predict the wild undulations that are about to occur as the dominoes fall from the Arctic south to our latitude. Initially, at least for the next few weeks, it appears 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 plunge into those areas, and you will likely hear reports of the news of record cold and snow from that side of the world.
When these disruptions are worst, we can usually have a 30-45 day period of harsh winter weather. For us, the time frame to look at is clearly the second half of January to mid-February. Can we descend to another historically cold and snowy stretch? Yes. But at this point I would say the odds are equally favorable for the worst consequences on the other side of the world, while our winter is dominated mainly by La Nina and more typical diurnal variations.
Either way, winter is far from over. Even in the most mild and benign weather patterns, we will have breaks from cold and snow here and there. The above discussion is just a “warning” that atmospherically big things are happening right now. A giant bowling ball has been thrown through the atmospheric lane, whether our pins stay put or not, remains to be seen.
The WBZ-TV weather team will closely monitor developments in the coming days and keep you informed of the pattern. We plan to have a full winter forecast update early in the week of January 18th, so stay tuned!
Follow Terry on Twitter @TerryWBZ