Roll cloud off coast of Brazil
The photo above showing a sinister looking roll cloud was taken aboard ship while en route from Paranagua, Brazil to Montevideo, Uruguay. Photographer: Capt. Andreas M. van der Wurff
Roll Cloud over Wisconsin
This is a type of arcus cloud called a roll cloud. 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. Photographer Megan Hanrahan.
St. Cloud Roll Cloud
This nasty looking roll cloud is taking dead aim on the St. Cloud Middle School in St. Cloud, Florida. Photographer: Jon Zenzel
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Roll Cloud Over Uruguay
Roll Clouds. 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. Potographer Daniela Mirner Eberl
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