Itx-Weather
Barometric Pressure, at Pembrokeshire:
Current Barometric Pressure and, Barometric Pressure history.
Weather data updated every 10 minutes.
Station Pressure:
This is the absolute air pressure at a given reporting station. The air pressure is the combined weight of all air located in a column directly above the reporting site. Consequently, the station pressure may vary tremendous in mountainous regions due to the strong variation of atmospheric pressure with height. Vertical variations of pressure range up to 150 mb per mile whereas horizontal variations are usually less than .1 mb per mile.
Sea Level Pressure:
The sea level pressure is a correction of the station pressure to sea level. This correction takes into account the standard variation of pressure with height and the influence of temperature variations with height on the pressure. The temperature used in the sea level correction is a twelve hour mean, eliminating diurnal effects. Once calculated, horizontal variations of sea level pressure may be compared for location of high and low pressure areas and fronts.
Pressure Tendency:
This is the change of sea level pressure with time. This is usually reported as a three hour pressure change in millibars.
Weather definitions curteousy of noaa.gov.
For the definition of Barometric Pressure from the BBC Weather Centre click here.
