Mid-latitude Cyclones Cheat Sheet by May100

Mid-la­­titude: 30° to 60° degrees N or S of the equator.
Cyclones: A low-pr­­essure system
They are also called extra-­­tr­o­pical cyclones or frontal depres­­sions

Mid-la­titude cyclones develop at the polar front, usually over the sea.
The polar front is where the cold polar easterlies meet the warmer westerlies of the subtro­pics.

- They consist of a pair of fronts (cold/­warm) linked to a central area of low pressure
- They carry a lot of moisture.
-Their winds spiral clockwise in the Southern Hemisphere
- Very large systems: up to 2000km across
- They travel eastwards (with the westerly winds in the westerly windbelt)
- Travel at 10km/h over areas of ±1200km per day
- Takes ±48 hours for the system to pass
- Occur in families of 3-5, and travel between 2-8 days apart

A stationary polar front forms. Wind shears in opposite directions along the front.

A 'wave' or a kink forms in the polar front as warm due to a distur­ban­ce/­fri­ction. Warm air is forced to lift up over cold air. Air pressure starts to drop and the warm and cold air masses begin to swirl alound the low pressure

The cold front bends, and a cold and form show develop.
The cold front leads the cold sector of air which pushes in the direction of the equator.
The warm front leads the warm sector of air which pushes in the direction of the pole.

Low pressure continues to intensify at the apex of the fronts.

An occluded front is a combin­ation of a cold front and a warm front.
A combin­ation of a cold front's tight bands of stormy weather and a warm front wide area of cloudi­ness.

Occurs when the coldest air in the MLC is behind the cold front.
The warm front is uplifted along the cold front.
The warm front and its air mass (the warm sector) lose contact with the ground.
The air is forced to rise, cool and condense (clouds form). Rainfall occurs with conditions similar to a cold front.
*The most common form of occlusion

When the overtaking cold front is lifted by the colder retreating air ahead of the warm front

It occurs when the coldest air is found ahead of the warm front. This causes the cold front to be uplifted along the warm front.
The air is forced to rise, it cools, condenses, and clouds form.
Rainfall occurs with weather associated with a warm front (temp rise, nimbos­tratus, contin­uou­s/heavy rainfall).