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polar vortex

Mild morning, but here comes the polar vortex again

Posted by David Epstein January 6, 2014 08:30 AM

There is a dense fog advisory this morning and you will need a bit of extra time getting around due to poor visibility and wet roads. The snow pack continues to rapidly shrink with a loss at my house of nearly 2 inches since 8PM last night. During the day more showers will pass through. For the evening commute the last batch of showers will be ending, so I expect fewer weather issues on the ride home than I do this morning. I’ll be tracking the showers and posting updates during the day on Twitter @growingwisdom

After 8PM, temperatures will have fallen below freezing so any slush that is left will freeze to a rock solid mass. Icy patches could develop on some roadways, but winds are going to be strong enough to dry the roads at the same time the cold air is rushing in to the area. This will greatly lessen the chances for any significant ice issues overnight.

Cold dry weather is in the forecast for the Tuesday and Wednesday when highs will be in the teens on Tuesday and upper teens and lower 20s on Wednesday. This cold snap won’t be as cold as the post snowstorm air when many areas saw temperatures fall below zero and wind chills reached 20 below.

You have no doubt heard about the extreme cold in the Midwest this morning. A piece of that cold will clip New England the next few days, but the core of the coldest air will stay west and south. Later this week, the jet stream retreats north and takes the arctic air along with it. A “January Thaw “pushes into the area for the weekend, and continues into the early to mid-part of next week.

All of this cold weather is a result of the position of the upper winds blowing across the planet. At 10,000 and 18,000 feet high in the atmosphere, strong winds carry weather systems, generally west to east in this part of the world. These belts of wind circle the globe. The highest level winds are known as the jet stream, but the winds at 10,000 feet, while related to the jet stream and lower, are very important in moving cold and warm air.

Across both polar areas of the planet there is a persistent whirling storm known as the polar vortex. This phenomenon is not new, and peaks in winter. Several times this winter the polar vortex has pushed southward into the United States and brought with it very cold air. The maps below show the position of the polar vortex today and again on Friday. Polar vortex Monday.png

By Friday, the core of the vortex is back in the arctic and taking the cold air with it. A few winters ago, the polar vortex sat over parts of Eastern Europe.
Polar vortex Friday.png

You may remember they had to contend with the coldest air in several generations that year. For those of you who remember your high school math, the numbers associated with the color on the map are standard deviations above or below where the winds would normally exist in early January. You can clearly see the core of the polar vortex is over 3 standard deviations below normal. That’s huge!

Notice temperatures on the map below. These are actual temperatures, not wind chill, at around 7PM this evening. You can see the subzero air has pushed very far to the south. The southward momentum of the air is good news for us here in New England. Because the core of the cold is moving south, then eastward, it means we will no experience the cold at the same levels as late last week. It’s certainly going to be frigid here Tuesday and Wednesday, but I unlike Saturday morning when subzero temperatures were commonplace, this week they will be an exception.
temp today.png

As the polar vortex retreats into Canada, the end of the week brings the start of a warming trend. We will be above freezing by Friday and even milder for the weekend. The Patriots game on Saturday looks to be played under cloudy skies a chance of showers with temperatures in the upper 30s! week weather.jpg If you click on the smaller image you will see a general forecast for the next week. Remember, this shows trends and once we get beyond a few days, the specifics aren't reliable, but the idea is pretty good.

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About the author

David Epstein has been a professional meteorologist and horticulturalist for three decades. David spent 16 years at WCVB in Boston and currently freelances for WGME in Portland, ME. In 2006, More »
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