•  Introduction:  examples of how to contour
•  Reminder:  check out Dr. Ackerman's contouring page on the web!

•  In-class exercise

Part I:  More about Isotherms
A) Remember that Isotherms are lines of constant temperature.
B) Reminders of the usefulness of isotherms:

•  Help us to see temperature advection
•  Often show where fronts are
•  Tell us a lot about what's happening in the future weather:
•  Increasing temperature contrast with time indicates the strengthening of a  front
•  Sinking/rising air on an isotherm map often show up as warm spots/cool spots

Part II:  Isobars
A) Isobars are lines of constant pressure.  This means that the pressure stays at the same value as you follow an isobar.
B) It may be helpful for you to think of isolines like a topographic contour map.  On a contour map, higher values denote higher ground--it is just the same with pressure maps and temperature maps--the higher values represent higher temperatures/pressures.
C) Some useful knowledge we can obtain from isobar maps:

•  For reasons we will explore more in the weeks following spring break, the wind tends to flow parallel to the isobars with lowest pressures always to the LEFT.  You can also think of this in terms of high and low pressure centers:  the wind flows in a clockwise circulation around areas of high pressure, and in a counterclockwise circulation around areas of low pressure.

•  Additionally, the speed of the wind depends directly on the spacing of the isobars.  Again, you can think about this like lines on a contour map.  Water flows from higher to lower regions, and flows at a faster rate down a steeper slope.  The same is true for the air--it could be said to "flow" at a faster rate "down" a steeper pressure slope.  Simply put, the closer the spacing of the isobars, the faster the wind will flow.
•  SO:  now, by looking at a map containing only isobars, you should be able to say a lot about the speed and direction of the wind!