downburst greater than 2.5 miles in diameter

Photograph by: Moller

A downburst is a strong downdraft which includes an outburst of potentially damaging winds on or near the ground and if the diameter of the downburst is greater than 2.5 miles, then it is called a macroburst. As a macroburst or a non-severe gust front passes overhead, the ragged, concave-shaped underside of the shelf cloud accompanies the onset of cold outflow winds at the ground.

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Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.