Weather

Air Masses and Fronts

Air Masses• Function of location (arctic – A, polar – P, tropical – T) and

surface type (continental – c and maritime – m)

Fig. 15.5

What do you notice about the pressure at the north pole?

What about at ~ 30oN and 60oN?

Why does this pattern occur, and what is happening?

Air mass movement

and consequences

Fig. 15.6

Daily QuestionUse a Venn diagram to compare and contrast the characteristics of warm fronts and cold fronts. Identify at least 7 features

1615

2 5 8 1012 14

3 4 7 911 13

• Cold Front• Air mass is cold

behind the front.• Advancement forces

the warm air up (rapidly)– clouds form

• Warm Front – • Air mass is warm behind the front• Warm is relatively stable – moves slower than cold

front• Slowly over take cold air (slight precipitation as front

passes)• Clear and sunny behind front prior to cold front• Stationary Front – front is moving very slowly• Occluded front – cold front has caught the warm front

Frontal Systems

Fig. 15.10

Fig. 15.12

Midlatitude Cyclones

• Regional Scale low pressure system

• A result of a collision of polar and tropical air masses

Fig. 15.13

• Generally start as a stationary front where cP air and mT air collide

Shearing causes

the northward

movement of

the tropical air and

the southward

movement of

the polar air to create a

counterclockwise rotation of the air masses.Fig. 15.14.a

• Warm air continues to migrate north and to the east

• Cold air continues to migrate south and to the east.

Cold air moves

about 2x faster

than warm air.

Thus, the cold

air will overtake

the warm air and

create a an

Occluded front.

Fig. 15.14.b

Fig. 15.14.c

Wave-cyclones & Mid-Latitude Storms

Deciphering a weather map

Tomorrow’s Weather

Wednesday’s Weather