What is a downburst? NBC6 meteorologist explains how they form – NBC 6 South Florida

This week’s weather coverage here in South Florida has been all about the Saharan air layer: the dust that follows the same winds that hurricanes follow from Africa all the way over to the United States.

The dust makes tropical development difficult, which we love. The dust also leads to some of our hottest “feeling” days, which is why we’ve seen heat advisories for feels-like temps well into the triple digits across all of South Florida.

Another aspect of the dust is its ability to cap storms from forming. Daytime heating causes warm air to rise, then cool and condense into rain. But when that rising air hits the Saharan air layer, storms can’t form. But when a storm does break through that cap, even if it is brief and isolated, it can be quite strong.

We saw that Wednesday about a mile from Redland. The Redland-Florida City-Homestead storm was the afternoon’s only strong storm, and it happened just after 3 p.m. There were reports of a tornado, and the video certainly shows destructive winds, but the NBC6 First Alert Weather Team was tracking this storm along with the National Weather Service.

The conclusion is that this was not a tornado, but a downburst that led to “straight-line” and not tornadic winds.

A downburst is a giant column of air that comes slamming down to the ground and spreads out in every direction. The estimated winds Wednesday were 50-55mph, which can certainly do the same damage as a weak tornado, but without the twisting. Wednesday’s straight-line winds were enough to knock down wooden powerlines.

Anna Harden

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