Friday, November 22, 2013

Wild 'Roll Cloud' Tumbles Across Texas Sky

via LiveScience
http://www.livescience.com
By Stephanie Pappas, Senior Writer



An other-worldly "roll cloud" stretching from horizon to horizon appears to tumble across the Texas sky in a new video.
The cloud video, taken by a couple in Timbercreek Canyon, south of Amarillo, Texas, shows a low, tubular cloud spinning horizontally like an upended tornado. As bizarre as this sight is, it has a meteorological explanation.
These tubelike cloud formations are a type of arcus cloud, a group of low cloud formations. Known as roll clouds, they sometimes form on the edges of thunderstorms. The storm's downdraft pushes cold air from the high atmosphere toward the ground, causing warm, moist air from the surface to climb upward as it is displaced. The moisture from this surface air condenses as it reaches cooler levels in the atmosphere, creating the cloud. Storm winds coax the condensation into a rolling, tubular shape that is often pushed far ahead of the rest of the storm.

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