Transcript occluded front. - Education Scotland

STANDARD GRADE
OCCLUDED FRONTS
John Smith Invergordon Academy
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.
FORMATION OF AN OCCLUDED FRONT
CUMULONIMBUS
Warm sector has been lifted off the
ground…
…so has the warm front
The Cold
Sector
(cold, dense
air)
HEAVY SHOWERS
OCCLUDED FRONT
THE EFFECT OF AN OCCLUDED FRONT (1)
CUMULONIMBUS
CUMULUS
CIRRUS
The Cold
STRATUS
Sector
(cold, dense
air)
Dense cool
air
LIGHT SHOWERSHEAVY SHOWERS
PERSISTENT
RAIN
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has been replaced by a section of the cold front.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.