1. STANDARD GRADE OCCLUDED FRONTS John Smith Invergordon Academy

2. WHAT IS AN OCCLUDED FRONT?
You have already learned that the cold front moves faster than the warm front.
The warm sector is squeezed upwards, so that is right off the ground.
The result is an occluded front. It is what happens when the cold front catches up with the warm front.

3. FORMATION OF AN OCCLUDED FRONT
HEAVY SHOWERS
The Cold Sector
(cold, dense air)
C O L D F R O N T
CUMULONIMBUS
Warm sector has been lifted off the ground…
…so has the warm front
W A R M F R O N T
OCCLUDED FRONT

4. THE EFFECT OF AN OCCLUDED FRONT (1)
HEAVY SHOWERS
The Cold Sector
(cold, dense air)
C O L D F R O N T
CUMULONIMBUS
CIRRUS
CUMULUS
STRATUS
W A R M F R O N T
Dense cool air
LIGHT SHOWERS
PERSISTENT RAIN

5. THE EFFECT OF AN OCCLUDED FRONT (2)
The approaching warm front looks normal – cirrus and then cumulus clouds, which bring rain.
The warm front does not reach the ground, it has been replaced by a section of the cold front.
There are no warm southerly winds at ground level. Instead, cold northerly winds are felt behind the cold front.
The warm sector, now pushed high up, cools. This is the end of the low pressure system, because there is no more warm air rising away from the Earth’s surface.