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 inHg (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 the 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.

To enter the calibrated relative pressure into the console, you must enter the SET mode. To enter the SET mode, press and hold the SET button for two seconds, and press SET  eleven more times until the pressure flashes. This setting allows you to change the units of measure from inHg to mm to hPa.

Press SET one more time, and Relative Pressure will flash.

Press [WIND +] or [PRESSURE -] to adjust relative pressure up or down.

Reference Section 6.4.4 of the User Manual below for details on calibration of relative pressure:

https://p10.secure.hostingprod.com/@site.ambientweatherstore.com/ssl/Manuals/WS-2902A.pdf

The settings are summarized below.

 

 

 

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