John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
The extremely rare formations appeared recently after a Colorado blizzard.
Normally, the only way you’d see horizontal icicles is if you’d been knocked on your keister and were viewing the world sideways. But Craig Stith recently had the fortune to stumble upon such improbable growths near Fort Collins, Colorado, snapping these photos so the rest of us can gawk at the weird sight.
Stith, a project manager at a nearby manufacturing site, recounts via email:
Following our blizzard on March 23, I noticed these icicles on a driving inspection of the grounds…. Winds were strong from the north. The icicles formed to the south of the sign post. Temps were moderate: high 20s or low 30s. Snow fell hard at times, mostly drifting, and visibility was low most of the day.
I’ve never seen this phenomenon before, and didn't see it on the other similar sign posts in the immediate proximity that day.
Here’s a close-up:
Stith shared these images with his brother Doug Stith, a sixth-grade science teacher in New Hampshire, who in turn got them featured as the Picture of the Day last Thursday at the Universities Space Research Association. There, Doug explains his theory on the conditions that birthed these reality-bending prongs:
Strong winds (40 mph or 64 kph), very moist air, and slightly below-freezing temperatures (near 30 degrees F or -1 C) played major roles contributing to the icicles' formation. Apparently, ice formed in holes on the inside of the metal signpost and was forced through the holes by the wind. You can see on the enlarged photo... that the icicles are positioned along the right side of the holes. The wind continued to push the moist air through the left sides of the holes, extending the length of the icicles that had already formed by the process of accretion. Note that there is minimal tapering of the horizontal ice unlike what's normally observed with vertical icicles.
This is at least the second documented case of sideways icicles (that weren’t caused by the movement of roof snow). Over at Schmetterling Aviation, in a post mostly about tinkering on an airplane, a man mentions almost in passing that horizontal ice-spikes were sprouting from the side of a hangar.