WRAL WeatherCenter Blog

# Where do I find out data on the prevailing winds in Chase City VA, and what does "prevailing" really mean? Does it mean that, since there are 4 major compass points, that if it comes out of the W over 25% of the time, it's the "prevailing wind"? Does it take over 50% to be prevailing? And where would I find a breakdown of what the winds are like over an annual period? Please send me a link so I can research this. I don't know where to start. You guys nail our local weather up here on the other side of "Kerr Lake" -Buggs Island Lake to Virginians - better than the Richmond stations. Thanks.

Posted August 5, 2007

MIKE MOSS SAYS:      Arthur,    Prevailing winds can be calculated a couple of different ways and the answer can vary a bit depending on the method employed. The most common way to determine the prevailing wind is to count up observations of wind direction at regular intervals (say, hourly) and then determine which direction occurs most often. That is the prevailing direction, and a wind speed can be determined by simple averaging of wind speeds from the same group of observations. Another method is to calculate a "vector averaged" wind in which each wind observation is decomposed into its north-south and east-west components, these components are averaged, and then the component vectors are combined to produce the average wind speed and direction. This method weights the "resultant" direction according to how strong the winds tend to be from each direction.

You will probably have a tough time finding a prevailing wind calculated for Chase City, but based on some surrounding stations it probably works out to be Southwesterly on an annual basis, with an average speed around 8-10 mph. You can look up monthly and annual prevailing direction and speed for several VA and NC locations in a publication from the National Climatic Data Center called "Climatic Wind Data for the United States." The pdf format publication is available for download at

http://www.ncdc.noaa.gov/oa/documentlibrary/wind/wind1996.pdf

You could also have a look at the Virginia State Climate Office web site, and possibly contact them for more detailed information. They are at

http://climate.virginia.edu/