The beauty, danger of ice storms
Ice storms are beautiful. And terrible. And dangerous.
They rarely are truly icy to deserve the name — a quarter-inch, a half-inch on tree limbs and bushes.
When that happens, the world is transformed into a breathtaking all-silver landscape.
But the weight of that ice can pull down power lines. They can do real damage to forests, tearing down limbs and snapping off tree tops.
“A quarter of an inch of ice, a half-inch, is a heavy load,” said Jeff Ward, forester with the Connecticut Agricultural Experiment Station in New Haven.
Town road crews hate them, said Fred Hurley, Newtown’s director of public works.
“That’s why we’re always watching what’s happening down in the Carolinas,” Hurley said of the ice storms that hit farther south.
The main problem with ice storms, Hurley said, is that they take a lot of work to keep up with. You can sand and salt one layer of ice, only to have another layer of ice sheet over that, he said.
And, he said, highway trucks are no different than cars on icy roads.
“I’ve seen trucks go up a hill and skid back down the hill,” he said.
Luckily, they are rare. A severe ice storm happens every 50 to 85 years, accord- ing to Lindsey Rustad of the US Forest Service. Lessdamaging but still substantial ice storms occur every five to 10 years, she said.
Rustad is part of a nationwide interdisciplinary project, funded by the National Science Foundation, to learn more about ice storms — meteorological events that have gone mostly unstudied.
The project’s computer modeling, taking climate change into account, don’t show we’ll get more frequent ice storms, Rustad said.
“But they do show the one’s we’ll get will be more severe,” she said.
Every winter, we get two or three episodes of glazing — very light ice forming, then melting by midday.
Areal ice storm rarely occurs, because it needs a set of very specific conditions. But those conditions can happen anywhere.
“Ice storms happen all over the world,” Rustad said. “They happen in China.”
“We rarely get them unless you get perfect conditions,” said Gary Lessor, director of The Weather Center at Western Connecticut State University in Danbury.
Those conditions are a blocking high to the north. Then, a layer of warm air has to sandwich itself into the mix midway up in the atmosphere.
Finally, a layer of subfreezing air has to lock itself in at ground level.
When precipitation falls, it starts out as snow. When it hits the warm layer of air, it melts, becoming rain. When it falls into the cold at ground level, it freezes on contact.
Heavy rain storms usually don’t cause ice storms, be- cause the rain washes away too quickly, said Bill Jacquemin, senior meteorologist with the Connecticut Weather Center in Danbury.
“What you need is a light rain,” he said.
The state’s most famous ice storm happened in December, 1973, covering the state with as much as an inch of ice and causing widespread power outages. The storm was so remarkable that Rick Moody celebrated it in a 1994 novel that became a 1997 film.
At the time, it was one of the most destructive storms the state had experienced.
“It was one of the most noteworthy storms in the state’s history,” Jacquemin said.
Another bad ice storm in November 2002, concentrated on Litchfield County, again pulling down limbs and causing people to lose power for two or three days.
Rustad of the US Forest Service has actually created ice storms on a test plot of New Hampshire by spraying forest plots with water until the ice accumulates on the tree limbs.
She’s found that with severe icing — a half-inch of ice accumulating on both sides of a branch — a tree will lose as many limbs in that storm as similar un-iced trees would lose in an entire year.
This matters in Connecticut right now because there are a lot of trees stressed by drought and insect infestation. In eastern Connecticut and in part of New Haven County, Ward said, drought and gypsy moth infestation have weakened oaks substantially.
And wherever there are ash trees in the state, there’s a good chance the emerald ash borer has been there, killing the tree off. Have an ice storm hit, and it will be in pieces.
“Ash is pretty brittle to begin with,” Ward said. “A dead ash has no structural integrity.”