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Faculty Experts Explain Science of Snowstorms, Ice Dams

Blame the Jet Stream for Cold, Snowy Winter in New England

UMass Lowell Image
Snow accumulation at UMass Lowell has exceeded 100 inches so far this season, with more fresh powder expected in the coming weeks.

02/27/2015
By Edwin L. Aguirre

The official start of spring is just a few weeks away — on March 20 — but Mother Nature is not letting up with the barrage of snowstorms and subfreezing temperatures on the eastern half of the country, especially New England. And this pattern is likely to persist for a while, according to a university weather expert.

“This February has already set a record for being the snowiest month since the 1928–29 winter, when our records for UMass Lowell began,” says Prof. Frank Colby in the Environmental, Earth and Atmospheric Sciences Department. “Our official snow total for the university for the season — from November to the present — is 107 inches. As for the cold, it’s not record-setting but we are much colder than normal. December was warmer than normal, but January was below normal and February so far is way below normal, by more than 10 degrees on average.”

Colby says the current weather trend is due to the pattern the jet stream has taken for the last seven weeks. 

“It’s similar to last year’s pattern, which was labeled the ‘polar vortex,’ ” he notes. “In reality, the jet stream always traces a wavy pattern across the United States. The jet stream may head south and east, and then turn back toward the north, making this wavy pattern. Typically, the jet stream pattern will be changeable, living up to the saying about New England weather:  ‘If you don’t like the weather, just wait a minute and it will change.’ ”  

When the jet stream is south of New England, residents experience colder than normal weather; when it’s to the north, the weather is warmer.

“When the jet stream dips south over the middle of the country and then swings north along the East Coast, we can get a nor’easter forming over the Atlantic, just off the coast,” he explains. “The pattern of the jet stream will steer the storm northward along the coast, and we can get a major snowstorm or blizzard.”  

For reasons that are the subject of current climate research, Colby says the pattern of the jet stream has been less changeable last winter and this winter, leaving us with long periods of cold and snowy weather.

“Some climate research appears to show that our warming climate may be causing or contributing to this behavior of the jet stream,” he says. “Whatever the reason, we’re having a remarkable winter so far.”

Snow Weighs Heavily on Homeowners

It’s not just the storms and brutal cold that New Englanders have to deal with. The mounds of heavy snow that have piled up on top of houses and buildings have already caused more than 100 roofs to collapse across the Commonwealth.

“New roofs built to standards don’t collapse right away, but as the structures age, they gradually lose their safety margin and can suddenly fail. That is why homeowners are encouraged to remove accumulated snow as soon as possible,” says structural engineering expert Tzuyang Yu, an associate professor in the Department of Civil and Environmental Engineering and director of the university’s Structural Engineering Research Group.

“Structures constructed with timber have more flexibility than those of concrete and steel. This means they can deform to some extent without collapsing. However, when they reach the point that they cannot bend or sag any further, after some period of time the roofs’ rafters and other components will fracture and the roof will collapse,” he explains. “Hire professionals when there is too much snow or the roof is too high.”

Yu says you can use the ceiling or attic floor to watch for warning signs of roof damage.

“If one sees excessive cracks or falling plaster or feels draft coming from the attic or roof, it’s time to take immediate action,” he says. “Also, if there are visible cracks or gaps between the roof and gable wall, do something right away.”

Many people use water leaks as an indicator, which is a good approach, even though timber houses can accommodate many leaks without collapsing, he notes.

“But it’s more conservative and makes people feel safe,” says Yu.

When snow melts, its density — and therefore its weight — increases dramatically.

“This doesn’t pose a problem to the roof if the water can be collected by gutters and flow down via downspouts,” he says. “The issue is the formation of ice dams because they stop the flow of water and turns melted snow into ice. When you see ice dams, it means there will be more ice stacking up on your roof. Remove them if possible.”

He adds: “When you see water leaks, depending on where, how much and how soon you see them, take appropriate actions. If leaks occur quickly after a snowstorm, then there is a good chance you have a hole on your roof.”