This New England winter: Record warmth, then record cold, then record warmth

Monitor staff
Wednesday, February 21, 2018

Concord, like many places in the Northeast, broke a warm-weather record Wednesday – shattered it, actually, with the highest temperature ever recorded during the month of February – but after living through an unusually warm early winter and an unusually cold midwinter, perhaps nothing should surprise us anymore.

The unofficial high at Concord airport Wednesday was 72, easily beating the previous record for the entire month of February, which was 69 degrees.

Similar records fell all over the eastern half of the country, with Boston recording the first back-to-back days in the 70s during any winter since the late 1800s, while it reached 48 degrees atop Mount Washington, tying the all-time record for any winter. Record highs for the day or the entire month were recorded in three dozen cities from southern Vermont through Ohio to New Hampshire, according to the National Weather Service.

But don’t put away the boots and gloves yet. It’s expected to snow here over the weekend, although we might see the dreaded “wintry mix” flipping between rain and snow.

“The increase in variability is part of what is expected with climate change, especially for the mid-latitudes,” said Mary Stampone, a UNH professor who is the state climatologist. (New Hampshire is as “mid-latitude” as it gets, since the 45th parallel, halfway between the equator and the North Pole, runs through Coos County.)

Variable doesn’t just mean warmer, although the trend is headed that way.

During the cold spell that hit the Northeast around New Year’s, Concord set a record on Dec. 28 with a daily high temperature of just 5 degrees. That was a whopping 9 degrees colder than the previous record for the lowest daily high temperature.

That cold midwinter followed a record warm autumn. September, October and November, the period known as “meteorological autumn” to weather watchers, was the warmest on record in Concord, according to the National Weather Service, which has kept track of temperatures there since 1868.

Things have been at least as wild in Portland, Maine, which like Concord, is overseen by the Weather Service office in Gray, Maine. During a two-week stretch between Dec. 28 and Jan. 13, it set four records for daily low temperature and one record for a daily high temperature.

“What we’re seeing – you can see in the data and it is projected to continue – is the increased frequency of abnormally warm days and a decrease in the frequency of those extreme cold days,” Stampone said. “We’ll still have them (record cold days) but they’re going to become less frequent, and days like today more frequent.”

“We also see this in November, on the other side of winter. There’s a greater frequency of getting up to 70 degrees in November,” she said.

Warmer winters can create a feedback loop that makes it even warmer by melting snow. Snow on the ground reflects more sunlight away, reducing the amount of solar energy that is retained and thus keeping it cooler.

“Once you have bare ground, you’re going to absorb more of that energy than when there’s snow,” Stampone said. This warmer ground makes it less likely for any future snow to stick around.

The region’s cold spells have been accompanied by extreme warmth in other parts of the globe – this was the fifth-warmest January on record for the planet as a whole, despite our shivering – as part of changes in weather patterns that have sent Arctic air unusually far south.

On Wednesday, temperatures in the Arctic were a staggering 45 degrees above normal, sending parts of Greenland and northern Canada above freezing during what is normally that region’s coldest time of the year.

(David Brooks can be reached at 369-3313 or dbrooks@cmonitor.com or on Twitter @GraniteGeek.)