Windrose

A wind rose is used by meteorologist and climatologist to give a brief  overview of how the wind speed and direction are related at a particular location. A polar coordinate system is used to monitor the frequency of winds over a long period of time. Different color bands are used to represent wind direction. The direction with the longest band is the primary wind direction.

Link: http://www.maine.gov/dep/air/meteorology/Windrosehome.html