1. Weather Air Masses and Fronts

2. Air Masses Function of location (arctic – A, polar – P, tropical – T) and surface type (continental – c and maritime – m) Fig. 15.5

3. What do you notice about the pressure at the north pole? What about at ~ 30 o N and 60 o N? Why does this pattern occur, and what is happening?

4. Air mass movement and consequences Fig. 15.6

5. Daily Question Use a Venn diagram to compare and contrast the characteristics of warm fronts and cold fronts. Identify at least 7 features Cold Fronts Warm Fronts 1.Warm air rises 2.Temperature decreases as front passes 3.Temperature increases as front passes 4.Cumulonimbus clouds associated with front 5.Cirrus clouds in advance of front 6.Associated with precipitation 7.Faster moving 8.Slower moving 9.Brings cP air in eastern U.S. 10.Brings mT air in eastern U.S. 11.Steeper slope of front 12.Less steep slope to front 13.Humidity decreases 14.Humidity increases 15.Moves from west to east 1 6 15 2 5 8 10 12 14 3 4 7 9 11 13

6. Cold Front Air mass is cold behind the front. Advancement forces the warm air up (rapidly)– clouds form Warm Front – Air mass is warm behind the front Warm is relatively stable – moves slower than cold front Slowly over take cold air (slight precipitation as front passes) Clear and sunny behind front prior to cold front Stationary Front – front is moving very slowly Occluded front – cold front has caught the warm front Frontal Systems Fig. 15.10

7. Fig. 15.12

8. Midlatitude Cyclones Regional Scale low pressure system A result of a collision of polar and tropical air masses Fig. 15.13

9. Generally start as a stationary front where cP air and mT air collide Shearing causes the northward movement of the tropical air and the southward movement of the polar air to create a counterclockwise rotation of the air masses. Fig. 15.14.a

10. Warm air continues to migrate north and to the east Cold air continues to migrate south and to the east. Cold air moves about 2x faster than warm air. Thus, the cold air will overtake the warm air and create a an Occluded front. Fig. 15.14.b

11. Fig. 15.14.c

12. Wave-cyclones & Mid-Latitude Storms

13. Deciphering a weather map

14. Tomorrow’s Weather

15. Wednesday’s Weather