1. Air Masses And Fronts The Air Outside Today, Was Somewhere Else Yesterday

8. What IS An Air Mass? An Air Mass is a huge body of air with similar temperature, humidity and pressure. They sometimes spread over hundreds of square miles.

9. Types of Air Masses There are 4 main types of air masses: 1) Polar 2) Tropical 3) Maritime 4) Continental Each has unique weather associated with it.

10. Tropical Air Masses Tropical Air Masses: Originate in tropics Originate in tropics Contain warm air Contain warm air

11. Polar Air Masses Polar Air Masses: Originate in polar regions Originate in polar regions Contain cool or cold air Contain cool or cold air Sometimes referred to as arctic air mass

12. Maritime Air Masses Maritime Air Masses: Originate over oceans Originate over oceans Contain moist air from evaporated ocean water Contain moist air from evaporated ocean water

13. Continental Air Masses Continental Air Masses: Originate over continents Originate over continents Contain dry air Contain dry air

14. 4 Major Air Masses of North America Maritime Tropical: Warm, Moist Air Maritime Tropical: Warm, Moist Air Maritime Polar: Cold, Moist Air Maritime Polar: Cold, Moist Air Continental Tropical: Warm, Dry Air Continental Tropical: Warm, Dry Air Continental Polar: Cold, Dry Air Continental Polar: Cold, Dry Air Where do each of these air masses originate?

18. Temperature dropped 20 degrees between 6AM and 11AM. WHY?

20. What Are Fronts? Fronts are areas where 2 or more air masses collide. Air with different temperature, humidity and pressure DO NOT MIX WELL.

21. What Are Fronts? An approaching front means a change in weather will occur. The change depends upon the approaching air mass.

22. Types of Fronts There are four types of front: 1) Cold Front 2) Warm Front 3) Stationary Front 4) Occluded Front

23. Cold Fronts Cold Fronts occur where cold air runs into slowly moving warm air. Cold air being more dense pushes warm air up. Warm moist rising air can cause clouds and storms.

24. Cold Fronts Cold Fronts: Often move quickly Can bring abrupt changes to weather (summer storms) Behind front is often cool and clear weather

25. Cold Fronts

26. Warm Fronts Warm Fronts occur where a warm air mass collides with a slower moving cold air mass. Because warm air is less dense, it rides above the cold air.

27. Warm Fronts Warm Fronts move more slowly than cold fronts so weather changes occur more slowly. In winter they often bring snow.

28. Warm Fronts

33. Stationary Front Stationary Fronts occur when cold air masses and warm air masses meet and neither move each other. May bring days of unsettled weather.

34. Stationary Front

38. http://www.cnn.com/2007/WORLD/asiapcf/04/02/quake/index.html