Determining Wind Speed From How Far Paper Blows

I know that there's a technique for estimating wind speed from the angle that a piece of paper takes on its way to the ground. If a 90 degree angle, there's no wind! A zero degree angle means the wind is exerting dramatically more force on the paper than gravity (not infinite, but enough that wind turbulence determines altitude more than gravity). I know that one of the scientists at the first atomic bomb test used this approach to make an approximate calculation of the energy release.

I suspect that somewhere there's a formula for doing this computation, based on the weight of the paper, its area, and the angle of fall. Do you know what it is? I have this suspicion that with enough time reading my physics text (Halliday and Resnick) I could probably derive it--but it has been enough time that I might end up deriving a formula that computed the wind speed at several thousands kilometers per second. (It's windy here, but not that windy.)

And yes, I've got the renewable resources bug again. It seldom stops blowing where I am--at least 15 mph right now, and often much higher. The question is how much higher? The wind sock at the airstrip up the hill from me would seem to indicate about 12 mph, because it isn't consistently horizontal. I also think we are getting a high wind here. My wife suspects we may be seeing Bernoulli principle at work, as the wind coming along the floor of the valley speeds up because of the constriction of the valley floor and walls where the valley rises to the pass. (The wind a bit higher up--where the windsock is located--doesn't have to speed up.)

I dropped a postcard from six feet up; it landed ten feet away. That's about a 30 degree angle.