High winds brought down a tree in a neighborhood on 18th Street in Bangor in this Nov. 1, 2019, file photo. Credit: LInda Coan O'Kresik

High winds knocked out power, downed trees and shut down schools late last month in the second extreme storm of the season. A few weeks before that, a nor’easter brought torrential rain and wind speeds up to 73 mph to coastal communities.

Extreme fall storms with high wind speeds and heavy rain have been uncommon in Maine — but that might be changing.

Since 2017, there have been three extreme storms, all resulting in hours of rainfall, high wind speeds, fallen trees and power outages. These storms are the result of climate change, according to Sean Birkel, a state climatologist and research assistant professor at the University of Maine’s Climate Change Institute in Orono. Based on climate projections, Maine might experience more frequent and extreme storms in the future.

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A set of baseline conditions — or boundary conditions — affect day-to-day weather. These conditions include sea-surface temperature, forest cover and snowfall. As the boundary conditions change — for example, the warming of the world’s oceans in the past three decades — the weather changes.

The loss of Arctic sea ice and warming ocean temperatures is fueling extreme storms in Maine.

“There’s nearly 50 percent less sea ice cover in the Arctic basin now than there was 20 years ago,” Birkel said. “The loss of Arctic sea ice has changed the circulation pattern of large-scale winds.”

The presence of warm air over the Arctic affects air flow, pushing cold air over Alaska, which in turn brings warm air to Maine and the Northeast.

The warming oceans in the Northeast also mean there’s more available moisture. As a result of these two factors, Maine has seen warmer fall temperatures and a tendency for more storms.

“Changing large-scale circulation [of wind] and warmer ocean water provides more fuel for an intense storm,” Birkel said. “The changes that have taken place support the hypothesis that intense storms could be increasing in frequency in fall.”

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Birkel and his team are working on detailed statistical analyses of storms to determine if and how the frequency has changed.

The Maine Department of Transportation is one entity that has noticed and had to deal with a change.

“If you look at the past several years, we have experienced more storms and more icing,” said Brian Burne, a highway maintenance engineer. “So, from a program standpoint, we have had to allocate more money towards winter maintenance and we have had to adjust contracts to ensure that we have enough materials on hand.”