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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 Question
Use a Venn
diagram to compare
3479
11 13
and contrast the
characteristics of
Cold Fronts
warm fronts and
cold fronts.
Identify at least 7
front
features 1.Warm air rises
2.Temperature decreases as
front passes
3.Temperature increases as
front passes
4.Cumulonimbus clouds
associated with front
5.Cirrus clouds in advance of
2 5 8 10
12 14
1
6
15
6.Associated with
precipitation
7.Faster moving
8.Slower moving
9.Brings cP air in eastern U.S.
10.Brings mT air in eastern
U.S.
Warm
Fronts
11.Steeper slope of front
12.Less steep slope to front
13.Humidity decreases
14.Humidity increases
15.Moves from west to east
Frontal
Systems
• Cold Front
• Air mass is cold
• Warm Front –
behind the front.
• Air mass is warm behind the front
• Advancement forces
• Warm is relatively stable – moves slower than
the warm air up cold front
Slowly over take cold air (slight precipitation
(rapidly)– clouds• form
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
Fig. 15.10warm front
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
Fig. 15.14.b
Occluded front.
Fig. 15.14.c
Wave-cyclones & Mid-Latitude
Storms
Deciphering a weather map
Tomorrow’s Weather
Wednesday’s Weather