Roll Cloud Over Ostrava, Czech Republic
June 03, 2010
The photo above shows a roll cloud tumbling over the southern part of Ostrava, Czech Republic, in conjunction with the passage of a cold front. It formed when a downdraft from a dying thunderstorm pushed cool, moist air along the surface just ahead of the front. The roll cloud, also known as an arc cloud, was rotating along its horizontal axis and winds were quite strong at more than 40 mph (64 km/h) while the cloud was passing by. Note how the shape of the cloud is similar to that of the structure at right. Photo taken on May 22, 2010.
Camera Maker: NIKON CORPORATION; Camera Model: NIKON D60; Lens: 18.0-50.0 mm f/3.5-5.6; Image Date: 2010-05-22 17:01:36 +0200; Focal Length: 31.0mm (35mm equivalent: 46mm); Aperture: f/7.1; Exposure Time: 0.0031 s (1/320); ISO equiv: 200; Exposure Bias: none; Metering Mode: Matrix; Exposure: Manual; Exposure Mode: Manual; White Balance: Auto; Light Source: Unknown; Flash Fired: No; Color Space: sRGB