Just when it seemed December couldn’t get any warmer, it has.
So far this month, virtually every day has featured above average temperatures. And not just by a few degrees, by a longshot in many cases. Christmas Eve may take the proverbial cake, with high temperatures soaring close to 70 degrees in many New England cities and towns. Not only is that nearly 30 degrees above normal, but it’s also as warm as many places were on the Fourth of July! Boston, for example, hit 72 on July 4 this year. Manchester, New Hampshire, topped out at 70 on Independence Day.
Before 5 AM, new high temperature records had already been achieved from Burlington, Vermont, to Providence, Rhode Island, and down to Bridgeport, Connecticut. Many more will be set over the course of the day.
So what’s causing the absurd warmth? A major shift in the jet stream.
Recall that the jet stream is the river of fast moving air that not only drives the storm track across the nation, but also separates warm and cold air. Typically that sits to the south of New England this time of year, keeping us on the chilly side. This year the jet stream has surged north, allowing the warmth to follow.
Northward shifts in the jet stream are quite common during El Nino patterns, which we are in. El Nino is a warming of equatorial waters in the Pacific, and even though that ocean warming is happening thousands of miles away it can have big implications here.
Along with El Nino, the polar vortex is very strong right now. The polar vortex is a ribbon of fast moving air that encircles the polar regions. When it’s strong, it keeps cold air locked around the Arctic. When it weakens, as it did quite regularly a few years ago, cold air floods the continental United States.
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For those of you waiting for traditional winter weather, there are signs of a pattern change as early as next week. That means cold and snow isn’t far off for parts of New England.
By then though, we’ll already have set a new record in Worcester, Massachusetts. So far this season the city has yet to receive measurable snow. Prior to 2015, the latest first measurable snow had been Dec. 24, 1923.
