"I thought it was squared. E.g. double the wind speed, quadruple the force."
No for some reason the standard 1/2 mv**2 doesn't apply in this case. I'm weak on hydraulics, but the data and formulae I've seen indicate a spread in wind load values, depending on conditions, with the power generally a product of the velocity cubed.
I can't find references other than the usual square of the wind speed. (That is, a 90 mph wind vs a 30 mph is nine times more destructive)