- Snow roller
A snow roller is a rare
meteorological phenomenon in which largesnowball s are formed naturally as chunks ofsnow are blown along the ground bywind , picking up material along the way, in much the same way that the large snowballs used insnowmen are made.Unlike snowballs made by people, snow rollers are typically
cylindrical in shape, and are often hollow since the inner layers, which are the first layers to form, are weak and thin compared to the outer layers and can easily be blown away, leaving what looks like adoughnut or jelly roll. Snow rollers have been seen to grow as large as two feet in diameter.The following conditions are needed for snow rollers to form:
* The ground must be covered by a layer of
ice that snow will not stick to.
* The layer of ice must be covered by wet, loose snow with a temperature near themelting point of ice.
* The wind must be strong enough to move the snow rollers, but not strong enough to blow them too fast.
* Alternatively, gravity can move the snow rollers as when a snowball, such as those that will fall from a tree or cliff, lands on steep hill and begins to roll down the hill.Because of this last condition, snow rollers are more common in hilly areas. However, the precise nature of the conditions required makes them a very rare phenomenon.
External links
* [http://www.torontoharbour.com/blog/snow-donuts-a-natural-weather-phenomena.html Snow Rollers in Toronto ]
* [http://www.oznet.ksu.edu/dp_wdl/snowroller1.asp Snow Rollers in Kansas]
* [http://www.crh.noaa.gov/ilx/events/roller.htm Snow Rollers in Central Illinois]
* [http://www.enquirer.com/editions/2003/02/13/tem_snowrollers13.html Snow Rollers in Cincinnati]
* [http://www.ksl.com/?nid=396&sid=135819&pid=40 Snow Rollers in Utah]
*cite news |last=Gilmore|first=Susan |url=http://seattletimes.nwsource.com/html/localnews/2003622603_donut17m.html |title=A rare treat from nature: Perfect snow doughnuts |publisher=The Seattle Times |date=2007-03-17 |accessdate=2007-03-19
*cite news |url=http://www.npr.org/templates/story/story.php?storyId=8993287 |title=Snow Doughnuts Are The Real Thing |publisher=National Public Radio |date=2007-03-19
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