Saturday, May 6, 2017

Surprise Wind Storm Blasts Parts Of Vermont; Widespread Damage Reported

Tree against a house in Rutland during Friday's high winds
Photo by Jennifer Holdren via WCAX-TV
A howling windstorm unexpectedly slammed parts of Vermont, especially around Rutland County late Friday afternoon and evening, prompting widespread power failures and quite a bit of damage.

More than 15,000 people lost electricity in Rutland County alone. Many, many trees fell. Lawn furniture blew away roofing shingles peeled off roofs and power flashes lit up the sky as lines and transformers failed.

As of 5:30 a.m. this morning, at least 10,000 customers were still without electricity in Vermont.

At least two houses were damaged by falling trees in Clarendon. 

Winds gusted as high as 74 mph in Wells, Vermont. South Pomfret had a gust to 61 mph and Mendon reached 56 mph. Based on damage reports, I bet other areas without anemometers made it past 60 mph.

Other areas of the state reported high winds as well: Many trees were down near Exit 3 on Interstate 89 a little northwest of White River Junction.

The wind extended north along the western side of the Green Mountains all the way north to Chittenden County, where roads were blocked by fallen trees in Jericho and Underhill.

The storm was a surprise: No wind alerts had been issued ahead of the storm, though the National Weather Service in South Burlington issued wind advisories, then high wind warnings and special weather statements as the gusts escalated.

The weather pattern that caused the damaging winds Friday does happen occasionally in Vermont. In fact some of these storms are worse than Friday's  like an even more destructive storm in Rutland on April, 2007.

Strong low pressure for this time of year was heading north toward the eastern Great Lakes. Air flow was from the east and southeast. The wind climbed over the mountains, then descended down the west slopes of the Green Mountains.

The winds gain momentum as they come over the mountains and descend down the west sides of the mountain slopes. That's how ou get your strong winds.

Often - and I think this is what weather forecasters expected - is a layer of stable air near the surface deflects the high winds to a couple thousand feet above the surface, so most people don't get the winds.

This time, the wind managed to have enough momentum to roar down the west slopes of the Green Mountains and slam into populated valleys near the base of these western slopes. So you got your high winds.

Adding to the trouble was the season. This type of storm is most common in the winter or early spring, when there are no leaves on the trees.

Trees are beginning to leaf out now. Each leaf acts like a little sail, pulling on tree branches as the wind hits them. This adds to the wind stress on the trees, making them more likely to break.

On top of that, it's been wet lately, so the ground is soft and mushy. That makes it easier for trees to get uprooted during strong winds.

This kind of storm is almost always pretty localized. A few miles away from the western slopes of the Green Mountains, everybody was probably saying, "What storm?" As Rutland and Underhill gusted away last evening, winds were dead calm at my house in St. Albans,  Vermont. The highest wind gust all day Friday in Burlington was just 19 mph.

For different reasons involving the same storm, there could be a little more wind trouble in Vermont this afternoon.

The storm is to our west now and the Champlain Valley will channel and focus southerly winds heading up the valley. Winds could gust to 35 to 40 mph or so, and that could mean some broken tree branches and maybe a few more power failures.

It won't be nearly as chaotic as Friday, but there still might be a little wind trouble ahead this afternoon.

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