Page 312 - PPL-engelsk 2025

Meteorology

3.8.7 Cold front

We have a cold front when a cold air mass meets a warmer air mass.

There are two types of cold fronts:

- Active

- Passive

The active cold front creates more severe and dramatic weather, while the

passive cold front results in milder weather, often only light rain or overcast

skies.

The diagram here shows

both an active and a passive

cold front.

3.8.7.1 Active cold front

In an active cold front, the cold air mass moves quickly forward, pushing the

warmer air upwards. This often results in heavy showers from cumulonimbus

clouds (CB) with showers, possibly thunderstorms, stormy weather, and

turbulence.

3.8.7.2 Passive cold front

In a passive cold front, the weather may resemble that of a warm front.
Because the cold air doesn’t move quickly, it gently pushes the warm air

upwards, causing it to condense into light rain or drizzle from nimbostratus

clouds.

As shown in the corresponding clouds (next page), clouds in a passive cold front

are also passive, meaning stratiform or extended clouds.

There is precipitation both before, during, and after the front. The clearing after

the front passes is slow. In some cases, fog may form in the precipitation after

the front has passed.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 312