An area of low pessure is called a depression:

• The low pressure of a depressions causes clouds and rainfall to form.
• Depressions therefore bring unsettled weather and rain.
• Winds are normally stronger, shown by the isobars being closer together.
• Depressions usually form over the Atlantic Ocean and are carried across Britain by westerly winds and move in an anticlockwise direction.

You can recognise a depression on a weather chart:

• the isobars are below 1000mb and are packed closer together
• a warm front (red line) is followed by a cold front (blue line)

You will learn more about warm and cold fronts in National 5 Geography