10/16/23, 11:55 PM Home - Evernote
CLIMATOLOGY
Mid-latitude Cyclones
General characteristics
Also called frontal depressions and extratropical cyclones
Move from west to east
Occur in the westerly wind belt
Air moves in a clockwise direction around the centre of a low pressure in the Southern Hemisphere
Often occur in families of 3 to 4 mid-latitude cyclones
Areas of formation
Develop at the Polar front between 40° and 60° N/S
The warmer westerly winds meet the cold polar easterly winds at the Polar front
Conditions necessary for formation
At about 50° N/S, a transition zone called the Polar Front separates the warm tropical air from the
cold polar air
This colder air pushes in underneath the warmer air while the warmer air gets pushed up over the
colder air
The isobars form in a circular pattern and a low pressure cell begins to form
Stages in the formation of a MLC
Initial Stage
The Polar front separates the cold Polar air from the south and the warmer subtropical air from the
middle latitudes
The two air masses do not mix easily because of their different characteristics
Development Stage
A frictional drag occurs between the cold and the warm air masses, disturbing the cold front
The warm, less dense air is pushed up by the cold, dense air. This results in a low pressure forming
Mature Stage
The air begins to rotate in a clockwise direction around the low pressure
The cold air pushes in under the warm air ahead of it and uplift occurs. A cold front leads the cold
air
The warm air rises up over the cooler air ahead of it and uplift occurs. A warm front leads the
warm air of the warm sector
Both fronts are associated with uplift, cooling and possible rain
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Occluded Stage
All the warm air has been lifted off the surface by the colder air
The warm sector becomes narrower as the cold front catches up with the warm front
The sector will be displaced above the cold air
The front is known as an occluded front
Dissipating Stage
The system weakens
Weather patterns associated with cold, warm and occluded fronts
Before and during a cold front
Wind changes from west to south west
Strong winds
Air pressure decreases as cold front approaches then increases as cold front arrives
Temperature decreases
Relative humidity is high during precipitation
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CLIMATOLOGY
Mid-latitude Cyclones
General characteristics
Also called frontal depressions and extratropical cyclones
Move from west to east
Occur in the westerly wind belt
Air moves in a clockwise direction around the centre of a low pressure in the Southern Hemisphere
Often occur in families of 3 to 4 mid-latitude cyclones
Areas of formation
Develop at the Polar front between 40° and 60° N/S
The warmer westerly winds meet the cold polar easterly winds at the Polar front
Conditions necessary for formation
At about 50° N/S, a transition zone called the Polar Front separates the warm tropical air from the
cold polar air
This colder air pushes in underneath the warmer air while the warmer air gets pushed up over the
colder air
The isobars form in a circular pattern and a low pressure cell begins to form
Stages in the formation of a MLC
Initial Stage
The Polar front separates the cold Polar air from the south and the warmer subtropical air from the
middle latitudes
The two air masses do not mix easily because of their different characteristics
Development Stage
A frictional drag occurs between the cold and the warm air masses, disturbing the cold front
The warm, less dense air is pushed up by the cold, dense air. This results in a low pressure forming
Mature Stage
The air begins to rotate in a clockwise direction around the low pressure
The cold air pushes in under the warm air ahead of it and uplift occurs. A cold front leads the cold
air
The warm air rises up over the cooler air ahead of it and uplift occurs. A warm front leads the
warm air of the warm sector
Both fronts are associated with uplift, cooling and possible rain
https://www.evernote.com/client/web?login=true#/note/8f0133e5-c4e5-f6f1-00f0-c90e48b69b01 1/15
, 10/16/23, 11:55 PM Home - Evernote
Occluded Stage
All the warm air has been lifted off the surface by the colder air
The warm sector becomes narrower as the cold front catches up with the warm front
The sector will be displaced above the cold air
The front is known as an occluded front
Dissipating Stage
The system weakens
Weather patterns associated with cold, warm and occluded fronts
Before and during a cold front
Wind changes from west to south west
Strong winds
Air pressure decreases as cold front approaches then increases as cold front arrives
Temperature decreases
Relative humidity is high during precipitation
https://www.evernote.com/client/web?login=true#/note/8f0133e5-c4e5-f6f1-00f0-c90e48b69b01 2/15
