Precipitation, Air Masses, and FrontsCurrent Weather

Finish Precipitation

Air Masses  

Fronts

For Next Class: Read Chapter 7 (pp. 215-227)

Reminder: Exam I next Friday! Review sheet is posted

Moisture Droplets

Figure 7.20

Raindrop and Snowflake Formation

Figure 7.21

Saturation Vapor Pressure

Figure 7.12

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Favorable conditions for freezing rain

Temperature conditions required for formation of

frozen, freezing, and liquid forms of precipitation

Cloud Types and Identification  

Figure 7.22

Atmospheric Lifting Mechanisms 

Figure 8.6

Orographic Precipitation

Figure 8.9

Orographic Patterns

Figure 8.10

Average Annual Precipitation

What is Rime Ice?

Rime IceA coating of tiny, white, ice particles caused by the rapid freezing of supercooled water droplets on impact with an object.

Rime Ice on Mt. Mitchell

Rime Ice on Beech Mountain

Heavy Rime

Icing on

Mt. Washington

Rime Icing on

Grandfather

Mountain

Snow Particle Photomicroscopy

Graupel

Snow Particle Photomicroscopy

Air Masses

What are the major air mass types and source regions?

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Air Masses

Classified as• Cold (polar, abbreviated as P) or warm (tropical or T)• Dry (continental or c) or humid (maritime or m)

Four basic types• Cold and dry, continental polar (cP)• Cold and humid, maritime polar (mP)• Warm and dry, continental tropical (cT)• Warm and humid, maritime tropical (mT)

Fifth type, arctic (A) air, is dry like continental polar air but colder

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Air Masses

Also differ in stability

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Fronts

Narrow zone of transition between air masses that differ in density• Density differences usually due to temperature

contrasts Warm and cold fronts

• Frontogenesis: fronts form or grow stronger• Frontolysis: fronts weaken