warm and occluded fronts. today cold fronts warm fronts occluded fronts

Warm and occluded fronts

Today

• Cold fronts

• Warm fronts

• Occluded fronts

Idealized Cold Front

Isotherms

0C 5 10 15 20 25 30C

100 km

Frontal Zone

44 75

COLDFRONT

Idealized Cold Front

Cross-sectional Characteristics

Cold Air

Warm Air

Strong Lifting near thefrontal boundary can produce convective clouds.

Idealized Cold Front

Cold Air Warm Air

Idealized Cold Front

• Precipitation:

– Located on either side of the front.

– Convective, showery in nature

– If warm air is stable

• Nimbostratus, Altostratus

– If warm air is unstable

• Cumulus, Cumulonimbus, Thunderstorms

Idealized Cold Front

© 1999 Prentice-Hall, Inc. -- From: Aguado and Burt, Understanding Weather and Climate

Cold Air Warm Air

Surface Front

Idealized Warm Front

Isotherms

30C 25 20 15

100 km

Frontal Zone

83

WARMFRONT

66

Idealized Warm Front

• Warm Front

– A boundary that moves in such a way that the colder (more dense) air retreats and is replaced by the warmer (less dense) air.

– The warm fronts tend to have weaker temperature gradients.

Idealized Warm Front

Cross-sectional Characteristics

Warm Air

Cold Air

Weaker lifting near thefrontal boundary oftenproduces stratiformclouds.

NsAs

Cs Ci

Idealized Warm Front

• Precipitation:

– Located on the cold side of the front.

– Stratiform, more persistent in nature

– In winter, precipitation may fall as sleet or freezing rain.

Idealized Warm Front

© 1999 Prentice-Hall, Inc. -- From: Aguado and Burt, Understanding Weather and Climate

Stationary Front

• Frontal boundary that either does not move or moves very slowly.

• Stationary fronts can “wash out” as the air masses on both sides of the front become the same.

Occluded Fronts

• Cold fronts typically move faster than warm fronts.

• Cold fronts can catch up and “overtake” a warm front.

• Depending on the different air masses, there are two types of occlusions:

– Cold type occlusion

– Warm type occlusion

Cold-Type Occlusion

Cold Air

Cool Air

Warm Air

Warm-Type Occlusion

Cold AirCool Air

Warm Air

Summary

• 4 types of front

• Weather comes with fronts