Hutton's formula

An empirical formula for determining wind pressure on surfaces inclined to the direction of the wind.

$P_{n}=P(sin\alpha )^{(1.84cos\alpha -1)}$

where

$P_{n}$ = the normal component of wind pressure

$P$ = the pressure per square foot on a plane perpendicular to the direction of the wind

$\alpha$ = angle of inclination of the surface with the direction of the wind