Multiplying 1.335 by the recording station's figure of 9.0 mph means that we can expect an average annual wind speed of 12.0 mph at our site. The one caveat in using this technique is the assumption that the recording station's anemometer is not surrounded by trees and buildings. If it is, the shear factor technique of estimating wind speeds does not work. Flagging Another useful tool to help determine the potential of a wind site is to observe the area's vegetation. Trees, especially conifers or evergreens, are often influenced by winds.
Strong winds can permanently deform the areas trees.
Flagging is usually more pronounced for single, isolated trees with some height. Pictured here is a pine tree in my yard with an obvious wind swept deformity. The upper part of the tree is swept back and away from the solar shower next to it. On the upwind side of the tree, the branches are noticeably stunted, on the downwind side, they're low and horizontal. The flagging was caused by persistent winds from, more or less, one direction.