What are high pressure systems?

High Pressure systems (anticyclones)

High pressure systems are huge areas of stable air. Air inside these pressure systems falls and as it does so it dries and warms up. This means that there is little or no cloud and therefore little or no rain.

Air moves clockwise around the centre of high pressure systems but isobars (lines of equal pressure) are well spaced meaning there is little or no wind.

Weather in high pressure systems is mostly dry with clear skies.

In summer this means warm, sunny days with occasional cirrus cloud.

In winter it means cold, dry days with very cold nights with the possibility of frost and sometimes fog. Sometimes stratus and nimbostratus clouds may develop giving a gloomy feeling to the weather.

Because high pressure areas are so stable they remain overhead for several days before moving away, blocking low pressure systems from reaching us.

This chart shows a High Pressure system sitting off the East coast of the UK on a summers day.A chart like this would mean high temperatures, little or no cloud  and light winds as the isobars are well spaced out.