Weather Fronts

In this lesson, we shall explain the different types of weather fronts.

What is a weather front?

A weather front is a boundary between two air masses. It can be thought of as the frontline in a battle, where the warm air represents one side and its ‘enemy,’ and the cold air, the other side.

Cold fronts

A cold front is symbolised on a weather map as a line with triangles. The triangles can be thought of as icicles. Cold fronts are often coloured blue.

The presence of a cold front means that cold air is advancing and pushing underneath warmer air. This is because the cold air is ‘heavier,’ or denser than the warm air. Cold air is thus replacing warm air at the surface. The tips of the ‘icicles’ indicate the direction of movement of the cold air.

Warm fronts

A warm front is symbolised on a weather map as a line with semicircles. The semicircles can be thought of as half-suns. Warm fronts are often coloured red.

The presence of a warm front means that warm air is advancing and rising over cold air. This is because warm air is ‘lighter,’ or less dense than cold air. Warm air is replacing cooler air at the surface. The edges of the ‘suns’ indicate the direction of movement of the warm air.

Occluded fronts

An occluded front is symbolised on a weather map as a line with both semicircles and triangles. They are often coloured purple.

These are slightly more complex than cold or warm fronts. The word occluded means ‘hidden’ and an occlusion occurs when the cold front ‘catches up’ with the warm front. The warm air is then lifted from the surface, and therefore hidden. An occlusion can be thought of as having the characteristics of both warm and cold fronts.