A depression is an area of low pressure which moves from west to east in the UK.
Low pressure systems can be identified from a synoptic chart due to:
In a low pressure system the warm front is the first to pass over. This occurs when warm air meets cold air and the warm air rises above it. Warm fronts bring steady, continuous rain.
The next front to pass over is the cold front. Cold fronts bring heavy rain showers.
When the cold front catches up with the warm front the result is an occluded front. Occluded fronts bring sudden downpours of heavy rain.
All three fronts are associated with rain.
Watch the following clip to help you make sense of weather fronts.
As a depression passes over the following changes occur.