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How to Measure Wind Speed & Central Pressure

Whether you're interested in meteorology or simply want to gauge the weather without a newscaster's help, you need two key pieces of information. The first is wind speed, which can tell you if there's a calm before a storm, gale winds blowing or light breezes coming your way. The second is central air pressure, which tells you what kind of air systems are in your area. When combined, wind speed and central pressure will almost always point you to an accurate weather forecast.

Things You'll Need

Anemometer
Liquid-filled barometer
Stopwatch

Instructions

- 1
  Set an anemometer out in the open, somewhere unobstructed by trees, bushes or buildings. The anemometer must be fully exposed to all the changes of the wind. These tools have four arms with fan blades or cups on the ends. The wind catches the cups easily and turns the anemometer with very little effort.
- 2
  Place a barometer next to the anemometer. Choose a barometer filled with either mercury or dyed alcohol. These barometers are old-fashioned compared to dial barometers, but they give very accurate readings.
- 3
  Wait for the anemometer to begin spinning; it shouldn't take much force. Use a stopwatch to help you count how many times the anemometer spins in one minute. Estimate 1 mph for every 10 spins. For instance, if the anemometer spins 30 times in a minute, the wind is moving at 3 mph.
- 4
  Check the barometer. The higher the liquid inside the barometer, the higher the atmospheric pressure. The lower the liquid, the lower the atmospheric pressure.
- 5
  Combine your findings to predict the weather. Low pressure systems usually mean storms are coming. If your anemometer is either totally still or spinning like crazy, there's a storm on the way. If your barometer reads high pressure and your anemometer is turning at a brisk-but-steady pace, the weather should be fine.

Nature