How Barometers Work & How to Accurately Use a Barometer

 

How do barometers work?

Barometers are very simple instruments, reflected by the fact many of us may have built very simple barometers when we were younger in school.

A barometer is typically a tube filled with mercury sitting upside down in a container filled with mercury (called a reservoir). When the atmospheric pressure falls, it presses down on the mercury in the container thereby forcing the mercury in the tube up. When atmospheric pressure is low, the mercury in the tube is allowed to flow back into the container.

Using Atmospheric Pressure to Predict Weather

Weather patterns are carried out in regions of high and low atmospheric pressure. By analyzing changes in weather pressure you can also analyze changes in weather patterns. The table below is a guideline for forecasting weather based on atmospheric pressure changes.

Atmospheric Pressure Weather Forecast Decreasing Storms, rain and wind together Rising Fair, dry, and cool weather Slow, regular decreases Strong changes in weather is likely Small, fast decreases Short lived rain and wind Fast drop in pressure over a short period of time Storm approaching within 5-6 hours Fast rise in pressure during average/above average pressure Pressure will soon fall, indicates poorer weather soon Fast rise in pressure during low pressure Predicts short lived fair weather Large sustained rise in pressure A long period of good weather will soon arrive