Weather forecasting is partly done by looking at the movements of ‘fronts’ – regions where warm air meets cooler air. The warm air at a front rises over the cooler air. This cools the warm air and so rain often falls near fronts.
Where warm and cool air meets, the warm air may become partly surrounded by cooler air. As warm air causes lower pressure, this creates a low pressure area called a ‘depression’. When a depression moves over us, we can expect unsettled, rainy or stormy weather.
A high pressure region called an ‘anticyclone’ form where cool air is surrounded by warmer air. An anticyclone moves slowly and can mean a long period of dry or sunny weather.
Bad weather can make driving very dangerous.
Movement of fronts
The region where cold air pushes against a mass of warm air is called a ‘cold front’.
The cold air burrows under the warm air (1) causing it to rise, and so clouds and rain are formed in the rising air.
The cold front catches up with a warm front, where warm air moves into a region of colder air (2). Here, the warm air rises over the cold air, causing more clouds and rain.
Eventually the cold air on the left catches up with the cold air on the right, and the warm air is lifted above ground level (3).
Finally, the warm air disappears, and we just see a region of cool air moving over a region of colder air (4).