1. Air Masses Fronts Cyclones/Anticyclones
Weather Patterns
Air Masses
Fronts
Cyclones/Anticyclones

2. Air Masses
Huge body of air w/similar:
Temperature
Humidity
pressure

3. Classifying Air Masses
Temperature
warm: tropical- form in tropics; low pressure
cold: polar- form in polar regions; high pressure
Humidity
humid: maritime- form over oceans
dry: continental- form over land in middle of continents

4. Four Major Air Masses Maritime Tropical Maritime Polar
Warm, humid air masses
Form over Gulf of Mexico & Atlantic Ocean- influence southeastern U.S.
West- form over Pacific Ocean
Maritime Polar
Cool, humid air masses
North Pacific & Atlantic Oceans
Affect west coast more than east coast; Why?!

5. Four Major Air Masses http://www. classzone
Continental Tropical
Hot, dry air masses
Form only in summer over Southwest & N. Mexico
Cover smallest area in U.S.
Continental Polar
Cool, dry air masses
Form over central & northern Canada & Alaska

8. Fronts
As air masses move, they bump into each other & do not mix easily.
Front- area where 2 air masses meet
Often cause storms & changeable weather
Type of front depends on characteristics of air masses & their movement

9. Cold Fronts
Rapidly moving cold air mass runs into slower moving warm air mass
Cold air slides under less dense warm air pushing warm air up
Move quickly causing abrupt weather changes
Clouds- cumulonimbus clouds, followed by altocumulus & clearing
After front- cool & dry

10. Cold Front Before During After Winds S-SW Gusty/shifting W-NW
Temperature
Warm
Sudden drop
Steadily dropping
Pressure
Falling steadily
Minimum, then sharp rise
Rising steadily
Clouds
Ci, Cs, Cn Cn Cu
Precipitation
Short showers
Heavy rains, possible, thstorms
Showers; clearing

13. Warm Front
Moving warm air mass collides with slowly moving cold air mass
Warm air moves over cold air
Humid warm air produces showers & light rain along front or scattered clouds if dry
May be foggy or rainy for several days
Clouds- cirrus, becoming cirrostratus; altostratus thickening & lowering becoming nimbostratus
After front- warm & humid

14. Warm Front Before While After Winds S-SE Variable S-SW Temperature
Cool-cold; warming
Steady rise
Warmer, then steady
Pressure
Falling
Leveling off
slight rise, then fall
Clouds
Ci, Cs, As, Ns, St, fog; occas.Cb in summer
stratus-type
clearing w/ scattered Sc; occas.Cb in summer
Precipitation
Lt.-mod. rain, snow, sleet, or drizzle
Drizzle or none
Usu. None, possl. lt. rain showers

18. Stationary Fronts
Cold & warm air mass meet, but neither has force to move the other
May produce rain, snow, fog, or clouds
May bring clouds & precipitation for many days

19. Occluded Fronts Most complex weather situation
Warm air mass caught between 2 cooler air masses
Temperature near ground becomes cooler
Warm air mass cut off or occluded
May be cloudy, rainy, or snowy
Clouds- warm sector: cumulus, stratocumulus

23. Cyclones Swirling center of low air pressure
Counterclockwise spin of winds towards low pressure
Associated w/storms & precipitation

24. Anticyclones High pressure centers of dry air
Winds spiral outward from high pressure spinning clockwise
Dry, clear weather

28. Quiz