MadSci Network: Earth Sciences

Re: Interpreting information from a barometer

Date: Fri Sep 1 01:26:23 2000
Posted By: Rick Neuherz, , meteorology, National Weather Service
Area of science: Earth Sciences
ID: 967180556.Es

A barometer is a device used to measure the pressure of the atmosphere at a 
location (essentially we are weighing the air column above the barometer). 
A barograph is a chart that provides a continuous pressure trace a location 
over time.  

The important thing with air pressure is the trend in the pressure.  
Generally speaking, falling pressure means that bad weather is on the way 
while rising pressure means that fair weather is on the way.  In addition, 
rapid changes in pressure are typically associated with windy conditions 
since these rapid changes are associated with large differences in pressure 
over an area. The larger (smaller) the difference in air pressure over an 
area, the stronger (weaker) the wind.

If you notice that the pressure indicated by your barometer is falling 
quickly, you might be in for windy conditions and rain (snow or ice if it's 
cold). If the barometer is falling slowly, the winds probably won't be very 
strong and you might just have cloudy skies rather than rain or snow.

Conversely, if the pressure is rising rapidly, you may experience windy 
conditions and quickly clearing skies (after it has been raining or 
cloudy).  If the pressure is rising slowly, the winds probably won't be as 
strong and it may take a while for skies to clear, if they do at all. 

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