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UNDERNEWS

Undernews is the online report of the Progressive Review, edited by Sam Smith, who covered Washington during all or part of ten of America's presidencies and who has edited alternative journals since 1964. The Review, which has been on the web since 1995, is now published from Freeport, Maine. We get over 5 million article visits a year. See prorev.com for full contents of our site

January 11, 2010

ROLL CLOUD



A Roll Cloud Over Uruguay
Photo by Daniela Mirner Eberl

NASA -These rare long clouds may form near advancing cold fronts. In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud. When this happens uniformly along an extended front, a roll cloud may form. Roll clouds may actually have air circulating along the long horizontal axis of the cloud. A roll cloud is not thought to be able to morph into a tornado. Unlike a similar shelf cloud, a roll cloud, is completely detached from their parent cumulonimbus cloud. Pictured above, a roll cloud extends far into the distance in 2009 January above Las Olas Beach in Maldonado, Uruguay.


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