The Midlatitude Cyclone

Cyclone Developmentbegins with a stationary front

Before Birth

Forecasting where on theStationary front the developmentwill occur is the tricky part!

Nascent stage ofCyclone Development

Birth andadolescence

Mature stageof Cyclone Development

Adulthood

Mature Wave Cyclone

Typical Cold Front Structure• Cold air replaces warm; leading edge is steep in fast-moving

front shown below due to friction at the ground– Strong vertical motion and unstable air forms cumuliform clouds

– Upper level winds blow ice crystals downwind creating cirrus andcirrostratus. Note change in wind and temperature as front passes.

• Slower moving fronts have less steep boundaries and lessvertically developed clouds may form if warm air is stable

Typical Warm Front Structure• In an advancing warm front, warm air rides up over colder air at the

surface; slope is not usually very steep

• Lifting of the warm air produces clouds and precipitation well inadvance of boundary

• At different points along the warm/cold air interface, the precipitationwill experience different temperature histories as it falls to the ground

The Partially OccludedStage beginswhen the cold front starts to overrun the warm front

Middle age

Partially occluded wave cyclone• Cold-occluded front

– Approach bringsweather sequencelike a warm front

– Frontal passagebrings weather morelike a cold front

• Warm-occludedfronts also possible

Cold-occluded front

Relationship between occluded fronts and Midlatitude cyclone development

Mature wavecyclone

Partially occludedwave cyclone

The Occluded Stageis characterized bymore warm air being pushed aloftand the size of thewarm air wedge at the surface decreases significantly

Over theHill

Relationship between occluded fronts and aMidlatitude cyclone

Partially occludedwave cyclone

Occluded wavecyclone

The final decay stageof the cyclone. The warmair is isolated aloft with cold air beneath.

Death

The Wave Cyclone Model(Norwegian model)

• Stationary Front

• Nascent Stage

• Mature Stage

• Partially Occluded Stage

• Occluded Stage

• Dissipated Stage