Straight line downburst wind from severe thunderstorms


Dauphin Island, Ala., (WKRG)

The Mobile office of the National Weather Service surveyed the storm damage on Dauphin Island, Alabama, from Sunday, May 12, 2019 and determined it was straight line winds. Those are also known as downburst winds because they come straight down from a severe thunderstorm as a burst. When they hit the ground, they spread out but move in a straight line. Winds were between 70 and 80mph which is the same as those of a weak tornado.

The impact is very similar and the sound of wind is the same when it gusts that high.

When a thunderstorm producing a downburst approaches, a building will get a wind from one direction. When the thunderstorm moves directly overhead, the winds can come from directly above. When it moves away, the wind will come from the other direction. Combine this with the forces of push and pull and lift that wind causes, and you may get a damage pattern where everything is moved all in the same direction or it the pattern may be more random, unlike that from the rotation from a tornado.

In other severe storms, some of the highest straight-line winds recorded have been over 100 mph.

WKRG-TV Chief Meteorologist Alan Sealls

Here is the preliminary storm report from the National Weather Service…

A bow echo associated with a severe squall line of thunderstorms moved across Dauphin Island, AL between 730 AM CDT and 800 AM CDT Sunday, May 12, 2019. A NWS Survey Team found damage consistent with significant straight line winds along a considerable portion of the Island. Damage consisted of metal roofs torn off of some structures, downed pine trees, and road signs that were blown over. Observed damage was all blown in the same direction with no visible evidence of tornadic convergence. The damage started on the west end of Dauphin Island and peaked just to the east of the Elementary School before lessening somewhat along the east end of the Island.


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