1. Air Mass & Air Fronts SPI 0607.8.4
Interpret meteorological data to make predictions about the weather.

2. Air Mass
An air mass is an extremely large body of air that is fairly similar in any horizontal direction and shares properties of temperature and moisture content at any given altitude.

3. Air Mass
Air masses can cover hundreds of thousands of square miles. The longer the air mass stays over its source region, the more likely it will acquire the properties of the surface below.

4. 4 general air mass classifications
Polar latitudes (P) - located 60° north and south toward the poles
Tropical latitudes (T) - located within about 25 degrees of the equator
Continental (c) - located over large land masses--dry
Marine (m) - located over the oceans--moist

5. 4 general air mass classifications

6. Air Fronts
A front is defined as the transition zone between two air masses of different density. The differences in density are most often caused by temperature differences or air masses with a different humidity as well.

7. Four types of air fronts
Cold Front
Warm Front
Stationary Front
Occluded Front

8. Cold Fronts
A cold front is defined as the transition zone where a cold air mass is replacing a warmer air mass. Cold fronts generally move from northwest to southeast. The air behind a cold front is noticeably colder and drier than the air ahead of it.

9. Cold Fronts

10. Cold Fronts
A cold front is represented by a solid line with triangles along the front pointing towards the direction of movement.

11. Cold Fronts

12. Warm Fronts
A warm front is defined as the transition zone where a warm air mass is replacing a cold air mass. Warm fronts generally move from southwest to northeast. The air behind a warm front is warmer and more moist than the air ahead of it.

13. Warm Fronts

14. Warm Fronts
A warm front is represented by a solid line with semicircles pointing in the direction of movement.

15. Warm Fronts

16. Stationary Fronts
When two air masses come together but neither can move the other, the boundary between them is referred to as a stationary front. It is difficult for meteorologists to predict the weather along a stationary front, though it often resembles that of a warm front.

17. Stationary Fronts

18. stationary Fronts
A stationary front is represented by a solid line with semicircles pointing in one direction and triangles pointing in the other direction.

19. stationary Fronts

20. Occluded Fronts
When a cold front overtakes and pushes a warm front up into the air, trapping it away from the ground.

21. Occluded Fronts

22. occluded Fronts
An occluded front is represented by a solid line with alternating triangles and semicircles pointing the direction the front is moving.

23. occluded Fronts

24. Fronts in Action