Weather

“That was one of the more bizarre and poorly forecast events I can remember in years.”

Twins Walden, left, and Stephen Maglione, 22 months, of Somerville, take in the sights Sunday as Chinese New Year is celebrated in Boston’s Chinatown. Pat Greenhouse / The Boston Globe

By John Waller

February 14, 2022 | 11:33 AM

You don’t have to rub it in.

They know.

“Welp….that forecast didn’t age well,” 7News’s Jeremy Reiner tweeted Monday morning. “At least Saturday verified with record warmth…….Call it even?!”

“Nothing but Valentine’s [love] for you trolls,” NBC10 Boston’s Pete Bouchard said. “Nope, didn’t see this much snow coming Friday. Nope, I’m not happy about it. Sometimes Mother Nature sneaks one by you.”

“Predicting the future is challenging, but also rewarding and at times like this storm… humbling,” Sarah Wroblewski of WBZ weighed in. “It’s always a learning process and an opportunity to push yourself forward after mistakes.”

Yes, Boston meteorologists underestimated Sunday’s snowfall.

For instance, here was the National Weather Service’s last expected snowfall map on Saturday:

The snowfall forecast as of 3:55 p.m., Saturday, Feb. 12. – National Weather Service

And here is their snow totals map Monday morning:

The snowfall totals on Monday morning. – National Weather Service

So what exactly happened?

Local meteorologist David Epstein said there were some hints on Saturday that the earlier forecasts had it wrong.

By Saturday, “the models were sort of onto the fact that there was going to be more snow,” Epstein said Monday on his Weather Wisdom podcast, which he titled, “Why The Heck Did It Snow So Much?”

Epstein said “lift” occurred Sunday morning when the cold air arrived, which caused the initial snowfall.

“Lift is necessary in the atmosphere in order to create precipitation and clouds, so if you see a cloud, there’s lift,” he said on his podcast. “Our lift [Sunday] with that first round of snow in the morning came from a temperature difference, and those two temperatures as they met, warm air is lighter, it went up, it cooled, it condensed, it formed snowflakes, and we got that little bit of snow and then we had the lull.”

WBZ Chief Meteorologist Eric Fisher also cited lift in a Twitter explanation Monday morning.

“That was one of the more bizarre and poorly forecast events I can remember in years,” he said.

Epstein said the unexpected totals Sunday night were partly caused by what he called a “hybridized Norlun Trough,” or, in layman’s terms, an arm that stuck out out to the west of the storm.

“The Norlun Troughs can get stuck, and so you can see snow hour after hour after hour after hour in an area,” he said.

Also, the conditions in the clouds were forming perfect snowflakes.

“If you look at the snow [Monday] morning, it’s basically like dust, because the snowflakes are perfect and, as they came down, the air [was] allowed to pile up between them, and so it really piles up quite a lot more than it would otherwise because it’s so light,” Epstein explained. “You know, like a pillow that’s really fluffed up, and you could compress this down and it’s not going to be a lot of water.”

Overall, Epstein admitted Sunday’s snow was “certainly not well forecasted.”

“This is the great thing about weather is that there’s still surprises, it’s still why you need people … looking at this stuff,” he said. “I also think that Saturday was just so beautiful it was hard to wrap your head around the fact, ‘Hey, we’re going to see up to half a foot of snow in so many areas.’”