Understanding High Pressure Systems

⛵ 1. What is a High Pressure System?

A High Pressure System is an area where the atmospheric pressure is higher than the surrounding air. While the average sea-level pressure is about 1013 millibars (mb), a high pressure system has pressure values above that relative to nearby areas.

Here’s how it works:

• Air behavior – In a high pressure system, cooler, denser air sinks toward the surface rather than rising. Because the air isn’t rising, it doesn’t cool and condense to form clouds, so these systems usually bring clear skies and stable weather.

• Weather effects – You can expect dry, calm conditions with plenty of sunshine under a high pressure system, which contrasts with low pressure systems that typically bring wind, rain, and unsettled weather.

• Rotation – Due to the Coriolis effect, high pressure systems spin differently depending on the hemisphere:

    • In the Northern Hemisphere, they rotate clockwise.

    • In the Southern Hemisphere, they rotate anticlockwise.

In summary, high pressure systems mean settled, calm weather with blue skies — the opposite of the stormy conditions often associated with low pressure.