Page 313 - PPL-engelsk 2025

Meteorology

Here is a sketch of a passive cold

front.

Note the cloud type (Ns).

Normally, visibility is good after the

passage of a cold front, but this does

not apply to passive cold fronts.

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3.8.8 Occlusion

When a cold front catches up with a warm front, an occlusion occurs. The

occluded front's cloud system is a mix of the warm and cold front clouds.

On weather charts, an occlusion is

indicated by a violet line or a line with
small barbs and loops.

There are two types of occlusions:

- Cold occlusion

- Warm occlusion

3.8.8.1 Warm occlusion

In a warm occlusion, the cold air behind

the front is warmer than the cold air in

front of the front. The warm air mass,

which is lighter, is lifted above the

colder air, which comes from both the

front and the original warm front.

This type of occlusion often occurs in areas with smaller temperature

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 313