Understanding Isobars

1. Understanding Isobars Julie Ann Hugick Eastchester M.S. This slide show helps you learn how to draw the isobars (lines of equal pressure) around high and low centers. It also shows the ways in which winds blow.

2. To convert abbreviated air pressure to mb:-Place a decimal point in front of right most digitIf # between 0 and 55.9, add leading 10If # is between 56.0 and 99.9, add leading 9Example: 078 07.8 1007.8mb

3. ISOLINE ACTIVITY: • In PEN, uncode each pressure: 103=1010.3 • In PENCIL, label the highest pressure H and the lowest pressure L. • 3. For theHdraw the following isobars: 1016, 1012, 1008 mb • 4. For the L draw the following isobars: 996, 1000, 1004 mb • 5. For each wind indicator- show wind movement.

5. 1016 mb H L

6. 1016 mb H L 1012 mb

7. 1016 mb H L 1012 mb 1008 mb

8. 1016 mb H L 996 mb 1012 mb 1008 mb

9. 1016 mb H L 996 mb 1012 mb 1000 mb 1008 mb

10. 1016 mb H L 996 mb 1012 mb 1000 mb 1008 mb 1004 mb

11. 1016 mb H L 996 mb 1012 mb 1000 mb 1008 mb 1004 mb

12. Follow up questions: Describe the wind motion in theH. Describe the wind motion in theL. In what area is the wind speeds the greatest? Winds go from ___ to ____ for pressure.

13. Summary • Winds around a High blow in a clockwise direction away from the center. (“The clock is high.”) Highs usually have fair weather. • Winds around a Low blow in a counter-clockwise and inward. (“The counter is low.”) Low pressure systems often have stormy or unsettled weather.