Barometric Pressure & Storms

Low-pressure systems can spur violent storms.

The march of incoming storms is often heralded by a plunging barometric reading, which measures the downward force exerted by the overlying atmosphere at a given point.

Unstable Conditions

Rising air is the key ingredient to most storms, because water vapor in ascending parcels of air can condense to form clouds and precipitation.

The Barometer

Such events will register as falling pressure on a barometer, simplistically because there is less "weight" to the overlying air.

Rotation

The Earth's rotation and atmospheric dynamics cause air to spiral around established high- and low-pressure centers. Cyclonic storms spurred by the latter can be large and violent, as in the case of hurricanes.

Warnings

The exact reading of a barometer--usually a measure of atmospheric pressure in inches or units called millibars--is not as important as how fast or by how much the readings drop. Rapidly falling values are a strong indication of an approaching system of unsettled weather.

Records

As of 2007, the lowest barometric pressure on record, according to USA Today, was 25.69 inches. This occurred in 1979 in the western Pacific, as Typhoon Tip raged.

References

• "The Audubon Society Field Guide to North American Weather;" David M. Ludlum; 1991
• USA Today Weather: Ask the Experts - Air Pressure

Resources

• National Weather Service: Storm Prediction Center