Depressions are usually known as lows. They could also be called cyclones but this would probably panic too many people watching weather forecasts. They are areas of low pressure that pass over Britain and are responsible for a lot of our weather.

Lows bring the following conditions.

• Windy weather
• Cloudy conditions
• Periods of rain, and in winter, snow
• Unsettled, changeable weather

It is easy to identify depressions on synoptic charts (weather maps).

• The isobars (lines joining places with equal air pressure) are close together
• The air pressure gets lower as you move into the centre of the low
• Frequently they have weather fronts

To be able to "read" a depression on a weather map it is important to remember the following points.

• Winds blow (more or less) parallel to the isobars
• The closer the isobars the faster the wind
• In the northern hemisphere winds blow anticlockwise around the centre of the low
• Fronts mean rain - warm fronts a long period of steady rain, cold and occluded fronts a shorter spell of heavy rain
• The temperature between the warm and cold fronts is higher than outside them - this hotter area is called the warm sector
• Usually depressions move west to east over Britain