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I keep watch on a Barometer in my house. It never seems to go into the lower ranges below 29.5 in. or 990 mb. I'm wondering if I'm calibrating it correctly. Every once in a while I'll adjust the reading to match a weather service report. Then I guess my real question is how come we never seem to see low adjusted pressures, say below 29 in.?
Chuck R.
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Barometers are used to measure atmospheric pressure. These can be useful for anyone wanting to keep a watch on weather. Pressure rises and falls are a good indication of what kind of weather may be coming your way.
Here in the mountain west, we adjust our barometers so they can be read at sea level. If we didn't do this adjustment then places like Salt Lake and Denver would constantly have lower pressure than the rest of the country. We must recall that pressure decreases as we go higher in the atmosphere. If we didn't adjust, it would make analyzing weather maps an enormous pain. Thus, we standardize the pressure and also this way, everyone understands the pressure readings and we can do our map analyses to help us forecast.
Pressure is typically read in units called "inches of Mercury" or in Hg. We use mercury inside the barometer so that's why it's not inches of something else. Forecasters use in Hg also but we use another unit called a millibar or hectopascal. Sometimes you might hear these units when you are watching a meteorologist talk about hurricanes.
The average of SLC's pressure is about 30.00 in Hg or what equates to about 1015.92 mb. Standard pressure across the US is a little less than this actually. Anyway, our pressures fluctuate typically between readings like 29 in Hg to 31 in Hg. Those are the extremes, so you can see that not often will we have a pressure reading of plain 29 in Hg. We commmonly use hundreths for pressure readings so an example would be 29.92 in Hg.
The lowest pressure ever at SLC was actually 29 in Hg which is 982 mb! That's really low. That's like a super strong area of low pressure. Areas of low pressure typically can strengthen and have readings around 990 mb but to get into the 980 range is pretty rare especially for this part of the country. Low pressure areas can intensify as the come out of the rockies. A city like Detroit for example, its lowest pressure on record is 28.24 in Hg or 960 mb! That's as low as some hurricanes get!
Our readings don't normally go that low in SLC, so the barometer you have usually isn't getting below 29 in Hg and that's totally normal. The lowest pressure ever recorded from a hurricane was in 2005 with Hurricane Wilma. The pressure reading was 882 mb.
Answered by KSL Meteorologist Dina Freedman.
