Snowmageddon churns along here in the Washington, DC metro area, preparing to bring us a possible 6-16 inches more of the white stuff (argh, Snowverdose!) today and tomorrow.
And as we prepare to break some snowiest winter records (just 10 inches shy of breaking the all-time record of 54.4” set in 1898-99!), we’ve also noticed the increasingly large, beautiful and rather worrisome icicles dangling precariously from rooftops, gutters, windows and power lines throughout the area.
To better understand how and why these frozen stalactites form, and if they really are dangerous, I emailed several snow and ice experts.
According to Richard Armstrong, a senior research scientist from the National Snow and Ice Data Center in Boulder, Colorado, icicles form:
“When the air is around freezing. Some areas not in direct sunlight will typically be below freezing, while the direct sun is melting ice and snow on more exposed surfaces. The melt water drips down along edge surface and refreezes in the cool air, forming a column of ice.”
Which is why we typically see them dangling from overhangs like gutters and tree branches.
Armstrong notes that good icicle weather is a compromise between too warm and too cold:
“If it is warm enough the air will be above freezing and the re-freeze part of the process will not occur – if it is too cold, the ice, on the roof for example, will not melt in the first place. In general, you might say the climate of DC is somewhat in between, not the Arctic, although I am sure it seems that way sometimes, and still more wintry than the climates just a bit to the south of DC – so a relatively good climate for icicles.”
As for why icicles come in all kinds of strange shapes and sizes, Armstrong writes that it depends on two factors:
“1) The shape of the feature on which the icicle is forming, smooth and straight, or irregular. And 2) If melt water is flowing towards the icicle from one direction, in a straight line, in contrast to flowing in from several directions at the same time and converging at one point.”
So should we watch out for these ice cubes of death?
“Clearly, falling icicles can be a hazard … Icicles may grow so large that they break by their own weight, or melt during warmer temperatures, and that increased melting may also cause them to break from their previous attachment point … I am certain there have been injuries and fatalities from icicles falling from buildings.”
And besides damaging us, how can all this ice wreck the wires and structures they’re hanging from? Kathleen Jones from the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) researches ice accumulation from freezing rain and supercooled clouds on overhead wires and communication towers. She writes:
“The combination of the ice load and the wind on ice load can break wires, cross arms, and poles and/or other supporting structures. Damage associated with icicles on roofs may be to vehicles parked next to the overhang. Icicles on roofs are also often associated with ice dams that may cause water to infiltrate under the shingles with possible water damage to the house or building and its contents.”
Ice dams, now? Eesh. And you think you’re safe in your car? Think again, says Armstrong.
“Another twist is very large icicles falling from cliffs along highways hitting cars. Where I used to work doing avalanche hazard assessment and forecasting along U.S. Highway 550 in southwestern Colorado, icicles have fallen and destroyed passing cars. The same methods are used to prevent the build-up of these icicles as are used in snow avalanche control along the same highway – artillery.”
Unfortunately, I haven’t needed any heavy ammunition to get rid of the ones hanging over my doorstep – just a good swipe with a broom handle. I know. Boring.
Pictured above are some icicle photos taken by Discovery News Editor-in-Chief Lori Cuthbert, plus one taken in front of my own house. Got some cool icicle photos of your own? Post them below in the comments section – while standing safely to the side of course! Or better yet, follow Kathleen Jones’ advice:
“When the CRREL ice storm team deploys to document the damage in a freezing rain storm, we wear hardhats in areas where ice and ice-covered branches may be falling from trees.”