Depressions
Weather fronts
A In meteorological terms, a depression is an area of low air pressure. is an area of low pressure which moves from west to east in the UK.
Low pressure systems can be identified from a A detailed weather map containing different lines and symbols. due to:
- A band of cloud formed when warm air meets cold air, and the cold air pushes the warm air upwards.
- A band of cloud formed when warm air meets cold air, and the warm air rises above the cold air.
- possible A band of thick cloud formed when the cold front catches up with the warm front.
- tightly packed Lines on a synoptic chart which join places of equal air pressure.
- isobars showing pressure decreasing towards the centre from about 1004mb
Warm front
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.
Cold front
The next front to pass over is the cold front. Cold fronts bring heavy rain showers.
Occluded front
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.
Depression characteristics
- Wind - winds blow anticlockwise in a depression and along the isobars; where isobars are close together, wind is strongest.
- Wet - where warm air meets cold air, the warm air is pushed upwards, it cools, condenses and clouds form.
- Temperature - in general, the An area of warm air between the warm front and the cold front in a depression. behind the warm front brings warmer temperatures and the An area of colder air that surrounds the wedge of warm air in the warm sector in a depression. behind the cold front brings cooler temperatures.
As a depression passes over the following changes occur.