Surface Isobars and Conceptual Wind Arrows, 1200 UTC Tuesday August 1997
(Page 528 in Reader)
The map shows the surface pressure distribution at 1200UTC Tuesday August 1997. The chart shows the whole United States. As discussed in class, the lines are isobars (lines that connect points that are experiencing the same atmospheric pressure, or weight, at a given elevation, in this case sealevel).
Take a look at the eastern Pacific (Click on Map To Get Full-Sized Version) and try to imagine how the winds are moving with respect to the area on the map west of Washington labeled with an "H."
Looks like the air is "trying" to move from this area of high pressure (called the "Pacific High" to the area of low pressure over southern California (called the "California Thermal Low" or the "North American Thermal Low").
The air attempting to move to that low has a BIG problem. There are mountains in the way.