How a Weather Vane Works

The Basic Idea

Weather vanes first appeared more than two thousand years ago. They let people know the direction the wind came from and served as an early meteorological tool. These devices consist of two parts, the first part contains the cardinal directions and the second part contains the pointer. The compass points will face the appropriate directions and the pointer will spin to face the direction that the wind comes from when the wind blows, according to the BBC's H2G2 website.

Equal Weight, Unequal Volume

The pointer is shaped in such away that the mass of each end is even but each end has different volumes. The wind pushed the side with the larger volume the direction the wind is blowing, and this in turn causes the lower volume end to point in the direction the wind came from. The direction of the wind makes certain types of weather more likely and allows the observer to make predictions about future weather. A weather vane will not work if the weights are not equal or the volume of each side is the same. Weather vanes in the shape of a rooster are called weathercocks.

Modern equipment improves on the forecasting accuracy of the weather vane. Weather vanes see modern use as ornamentation for many buildings. Meteorologists will use a device called an aerovane that tells them which direction the wind comes from and can measure the wind speed, according to USA Today.

The surrounding environments help meteorologists know what kind of weather to expect when the wind comes from a certain direction. In Pennsylvania, for example, air coming from the south generally means that the temperatures rise. Air coming from the north generally means cooler temperatures. Meteorologists will use both air speed and wind direction over a period of time when making forecasts, according to The Weather Prediction website.

References

• How Traditional Weathervanes Work
• How Aerovanes Work
• Wind Direction and Weather Forecasting