Roll Cloud

Photo credit - pepe

Photo credit – pepe

Cloud of the Day – Roll Cloud

Roll cloud is a form of arcus cloud, defined as a low, horizontal cloud formation. Roll cloud is the milder of the two forms of arcus cloud. The other, shelf cloud, is often associated with violent weather. Roll clouds get their name not only from their appearance, but also from the fact that they seem to roll around their horizontal axis.

Photo credit - Daniela Mirner Eberl

Photo credit – Daniela Mirner Eberl

 

 

They are formed when a downdraft from an approaching cold front pushes warm, moist air up in front of it. If it goes over top and gets pushed down again, it can set up a circulation. If the warm, moist air is cooled to the condensation point, a roll cloud forms.

Photo credit - Dan Bush

Photo credit – Dan Bush

 

 

 

 

Queensland, Australia is blessed with predictable, relatively frequent appearances of normally rare roll cloud, which they call Morning Glory Cloud. They can be seen every October, the result of seasonal patterns of ocean and atmosphere. The link will take you to a video compiled from footage shot by Rob Thompson over a seven year period. This link will take you to a YouTube video shot in Texas.

Photo credit - Todd Mask

Photo credit – Todd Mask

 

 

 

 

 

Roll cloud is harmless, but it might presage weather with the advancing cold front.

rjb

About arjaybe

Jim has fought forest fires and controlled traffic in the air and on the sea. Now he writes stories.
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2 Responses to Roll Cloud

  1. Laird Smith says:

    Is there any particular wind direction with roll cloud?

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