1. Air Masses and Fronts Warm Up: What type of rock is formed from cooling lava?

2. Air Mass VIDEO Clip

3. Air Masses Air masses have the same properties as the surface over which it develops: Maritime = Wet Continental = Dry Polar = Cold Tropical = Warm mP = wet/cold cP = dry/cold mT = wet/warm cT = dry/warm

4. Air Masses in North America

5. Fronts A front is the boundary where two air masses meet. Types of fronts: 1.Warm Front 2.Cold Front 3.Occluded Front 4.Stationary Front WARM AIR COLD AIR FRONT

6. Front VIDEO Clip

7. Cold Front Cold dense air pushes under a warm air mass. The cold dense air moves faster and causes the warm air rises quickly. Narrow bands of violent storms form.

8. Why do cold fronts bring heavy rain and storms? Cold air interacting with warm air = a sudden drop in temperature = CONDENSATION occurs quickly and a fast difference in pressure Creates cumulonimbus clouds Cold dense fast moving air = high winds What you see in a weather map!

9. Cold Front Video Clip

10. Warm Front Warm air slides over departing cold air. Large bands of precipitation form

11. Why do warm fronts bring mild weather? It’s more difficult for the warm air to move against the cold dense air so there is a gradual difference in pressure and temperature What you see in a weather map!

12. Warm Front Video Clip

13. Occluded Front Two cold air masses merge and force warm air between them to rise quickly. Strong winds and heavy precipitation will occur.

14. Why do occluded fronts bring heavy rain and storms? Cold air that is more dense moves into an area of low pressure = CONDENSATION occurs quickly Forms cumulonimbus and nimbostratus clouds What you see in a weather map!

15. Stationary Front Warm and/or cold front stops moving. Light wind and precipitation may occur across the front boundary.

16. Why do stationary fronts bring long light precipitation? Neither front is strong enough to move the other Can stay put for days Differences in temperature = rain or snow What you see in a weather map!

17. Cyclones and Anticyclones Areas of HIGH and LOW pressure Cyclone = LOW PRESSURE = spin counterclockwise = associated with storms and precipitation Anticyclone = HIGH PRESSURE = spin clockwise = associated with fair weather.

18. Cyclones and Anticyclones in the USA

19. Cyclone Video Clip