Shelf Cloud Spotted Monday (Aug. 17)

August 17, 2015: Strong thunderstorms with heavy rainfall swept through the Stateline. One of those strong thunderstorms brought an interesting and eerie sight to the Rockford area. A shelf cloud rolled through ahead of a blast of heavy rainfall. Here’s what one looks like:

Shelf cloud, viewed from E. State St., Rockford, on Aug. 17, 2015. Courtesy: Josh Morgan

Shelf cloud, viewed from E. State St., Rockford, on Aug. 17, 2015.
Courtesy: Josh Morgan

These can be seen when strong thunderstorms form with strong winds and heavy rain. The shelf cloud forms when a strong downdraft of rain-cooled air hits the ground and spreads out from the storm, causing gusty winds.

Click on image to enlarge.

Click on image to enlarge.

When the downdraft winds cut underneath the warm updraft feeding the storm(s), a cloud can form in between the two.

Click on image to enlarge.

Click on image to enlarge.

The cloud gets the “foot” or “shelf” shape because of the warm air sloping up into the storm, with the downdraft carving it from underneath.

Click on image to enlarge.

Click on image to enlarge.

The underside of the shelf cloud can be jagged looking because of the turbulent winds.  These jagged clouds can sometimes hang down from the underside of the shelf cloud and look like funnel clouds.  Plenty of people see this and get spooked, thinking it’s a tornado. Important: remember to look for vertical rotation; if the cloud isn’t spinning like a top, it isn’t a funnel cloud or a tornado.

As always, thanks to everyone for sharing pictures of today’s shelf cloud!  Remember, though, to be smart and take those pictures safely!

-Alex

 

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Posted under weather

This post was written by Alex Kirchner on August 17, 2015

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