downburst less than 2.5 miles in diameter

A downburst is a strong downdraft which includes an outburst of potentially damaging winds on or near the ground. If the diameter of the downburst is less than 2.5 miles, it is called a microburst. The diagrams below depict the evolution of a microburst.

A microburst initially develops as the downdraft begins its descent from cloud base. The downdraft accelerates and within minutes, reaches the ground (contact stage). It is during the contact stage that the highest winds are observed. During the outburst stage (above), the wind "curls" as the cold air of the microburst moves away from the point of impact with the ground. During the cushion stage, winds about the curl continue to accelerate, posing a great threat to nearby aircraft.

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