Hutton's formula

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

P_n = P (sin \alpha)^{(1.84 cos \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