A very common wind speed frequency profile is in the shape of a Raleigh distribution which also equates to the 2 parameter Weibull distribution with the shape parameter equal to 2. The Weibull distribution is a generalization of the Rayleigh distribution and more information about Raleigh and Weibull distributions can be found on the following Wikipedia pages:

• Rayleigh Probability Distribution
• Weibull Probability Distribution
• Gamma Function Table for calculating the mean of a Weibull Distribution

One of the most famous plots of yearly wind speed distribution and available power is the 2002 Lee Ranch Wind Resource Assessment shown below.

• Lee Ranch Wind Speed Assessment Detailed Report

An interesting property of the Rayleigh and Weibull (shape par=2) distributions is that the mean (average) wind speed (v) and the wind speed of mean power (a function of v³) are constantly related by approximately a factor of 1.75. Whereby, for a mean wind speed of 4m/s, the wind speed for mean power output will be 4m/s * 1.75 = 7m/s. For an mean wind speed of 8m/s, the wind speed for mean power output will be 8m/s * 1.75 = 14m/s and so on.

Three Plots below illustrate the relationship: