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Figure 27- cold front occlusion and warm front occlusion Figure 28 – symbols used for Fronts


Cold front occlusion

Warm front occlusion

Occurs when the cold air which overtakes the

warm air is colder than the retreating cold air

Occurs when the retreating cold air mass is

colder than the advancing cold air mass

In the initial stage, weather system of the warm front persists. At the later stages the weather conditions resemble those of the cold

front.


Overtaking cold airmass plows under both air

masses

Advancing cold air being relatively less dense

overrides the retreating cold air mass

Table 6 – Occluded fronts – difference between cold front occlusion and warm front occlusion

7. Cyclones

The atmospheric disturbances which involve a closed circulation about a low pressure centre, anticlockwise in the northern atmosphere and clockwise in the southern hemisphere are called cyclones. They fall into the following two broad categories: (a) Extra-tropical and (b) tropical cyclones.