High pressure and anticyclones
A high pressure system is called an anticyclone.
- Air falls in an anticyclone so no clouds are formed.
- In summer, high pressure usually results in clear skies, gentle breezes and fine weather.
- In winter high pressure leads to clear skies and colder conditions.
- There is less wind as the isobars are further apart
- Anticyclones tend to move in a clockwise direction.
You can recognise an anticyclone on a weather chart as the isobars are above 1000mb and spread further apart.
Anticyclones tend to last longer than depressions. For example, an anticyclone can last for two weeks whereas a depression lasts 2-3 days.
Question
The synoptic chart below describes the likely weather conditions in Glasgow (G) and Lyon (L).
Explain the weather conditions experienced at Glasgow and Lyon on 14 November 2010 .
Look at the same synoptic chart now with some hints added.
Glasgow’s weather is very unsettled because a depression is passing due to low pressure.
The depression will bring rain.
The wind will be strong because the isobars are close together.
Wind direction will be south-westerly, blown anti-clockwise in a depression.
Lyon’s weather is settled as it is covered by an anticyclone due to high air pressure.
Lyon will be experiencing dry weather and clear skies.
The wind will be calm/gentle as isobars are far apart.
Wind direction will be easterly blow clockwise in an anticyclone.
