The feathery blue line is a dry squall blown out from a thunderstorm off to the southwest that is collapsing causing the descending air to strike the ground and drive out towards NE.
The wind velocity in this “dry squall” also referred to as a “white squall” was 20+ knots when it reached us, jumping from essentially calm conditions.
We encountered one of these on the Chesapeake with 37 knots of wind. The only warning we had was a coppery sky to the west, a rapidly approaching line of white disturbed water and the sound of trees rustling when the nearest trees were eight miles away.
Much higher velocities have been reported offshore.
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