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5.5 Barometric Pressure
Note: The weather station console displays two different pressures: absolute (measured) and
relative (corrected to sea-level).
To compare pressure conditions from one location to another, meteorologists correct pressure to
sea-level conditions. Because the air pressure decreases as you rise in altitude, the sea-level corrected
pressure (the pressure your location would be at if located at sea-level) is generally higher than your
measured pressure.
Thus, your absolute pressure may read 28.62 inHg (969 mb) at an altitude of 1000 feet (305 m), but
the relative pressure is 30.00 inHg (1016 mb).
The standard sea-level pressure is 29.92 in Hg (1013 mb). This is the average sea-level pressure
around the world. Relative pressure measurements greater than 29.92 inHg (1013 mb) are
considered high pressure and relative pressure measurements less than 29.92 inHg are considered low
pressure.
To determine the relative pressure for your location, locate an official reporting station near you (the
internet is best source for real time barometer conditions, such as Weather.com or Wunderground.com),
and set your weather station to match the official reporting station.
Note: This is a continuation of the previous section. To enter this mode, you must begin at
Section 5.1 and proceed to this section.
Press the
menu key to enter the Pressure Mode. You can skip over any setting by selecting the enter
key.
Figure 15
1. Relative vs. Absolute Pressure Display. Press the up key or down key to alternate the
display between relative (rel) pressure and absolute (abs) pressure.
2. Pressure Units. Press the enter key to set the pressure units. The pressure units will begin
flashing.
Press the up key or down key to alternate the display unit between hPa, inHg and mmHg.
3. Relative Pressure Calibration. When Absolute (abs) pressure is selected, this step will be
skipped.
Press the enter key to set the relative pressure calibration. The relative pressure will flash.
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