Ticker for July 22, 2008

                
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High Pressure: Nobody's Hero

More from the Ticker mailbag:

"Why do high pressure systems bring cool dry weather?
Why don't we have more of them?"

Well, when it comes to pressure systems, it's all about location.
And timing. And height. And season.

It turns out that, yes, when we think of the typical, refreshing
"cooler, drier air settling in" situation, that these air masses
are associated with high pressure systems. At the surface, anyway.

But, ask the folks in the southeast U.S. if the surface high they're
experiencing right now is refreshingly cool:



Surface high pressure systems are generally associated with large
air masses characterized by sinking (i.e., boring weather,
generally). In our (Oklahoma's) part of the world, during most of
the year, these slowly sinking air masses often originate as
refreshingly cool (or cold!), crisp air masses over Canada. When
they migrate southward, they bring most of their Canadian
characteristics with them, eh. However, in the summer, these
surface highs can be nasty, in a sweaty and oppressive kind of way.

And, if you jump from the surface to the upper parts of the
atmosphere, high pressure areas (often called "ridges") are
typically associated with warming processes. Depending on how you
view the chicken-egg relationship between upper-air features and
surface trends, these "ridges" can be considered escorts and/or
evidence of warmer conditions below.

In fact at this very moment, Oklahoma's 100 degree temps are being
watched over by a gimungous upper-level ridge:

Surface: 

Upperair: