Ticker for June 19, 2008

                
MESONET TICKER ... MESONET TICKER ... MESONET TICKER ... MESONET TICKER ...
June 19, 2008      June 19, 2008      June 19, 2008      June 19, 2008



Ticker: Back to Basics June

As most of you know, new Ticker subscribers get a semi-automated
response survey. Yes, the Ticker is semi-automatic, which might
explain the seven-day waiting period that the new sign-ups face.
Then again, maybe there's another reason.

Anyway, the contents of that message ask for a few favors. We ask
folks to help with Ticker word-of-mouth (tell a friend if you like
the Ticker ... better yet, tell our boss).

We also ask for specific topics to cover. Well, we had a very
generous reply this week from new subscriber "Ann" who dispensed
with the typical demure deferment and suggested no less than nine
topics.

And here's the thing: they're all great topics; ones that we think
are important to people's everyday lives, and everyday curiosities.

So, sincere thanks from us, Ann. We'll take them a few at a time
over the next few weeks, weather conditions permitting.

Topic: "Why is Oklahoma so windy?"

Great question, probably asked often during spring (and perhaps
embellished with some expletives ... thankfully, Ann avoided them).

Here's a partial answer:

In almost all situations, the strength of wind is directly related
to the magnitude of the pressure gradient. The pressure gradient is
how rapidly the pressure changes over space (from one location to
another). The stronger the gradient (more rapid the change), the
stronger the wind.

Fluids move from high pressure to low pressure. An expensive and
messy way to demonstrate this to yourself is to take the cap off
the toothpaste and apply pressure to the tail end. You'll see the
direct result of a pressure gradient moving a fluid. Push harder
(increase the pressure gradient) and the fluid flows faster.

(insert ketchup-packet-versus-rolling-tire warning here)

Air - being a fluid - works the same way: large pressure gradients
drive more rapid motion. But here's the catch: the earth's rotation
deflects large-scale atmospheric motions so that they flow mostly
*along* the pressure contours. So, winds flow counter-clockwise
around lows and clockwise around highs (don't share this Ticker
with anybody in the southern hemisphere, it will confuse them).

Anyway, even though air flows *around* surface pressure systems,
its speed is still directly related to the strength of the
pressure gradient.



This image shows a low-pressure system centered over Iowa. Notice
how winds are stronger (longer arrows) where there's a tighter
pressure gradient (where the yellow lines are closer together).

And that's where Oklahoma comes in. We live, work and do business
in a part of the globe that often sees low pressure systems develop
to our west and northwest in the lee of the Rocky Mountains.

As these systems strengthen, their pressure drops, which increases
the pressure gradient, which encourages stronger flow. If we're having
a howler of a windy day with southerly winds, you can bet that there's
a strong or strengthening low pressure system to our west.

It also turns out that we usually need fairly strong systems to
flip our winds to the north. So we typically see northerly winds
come in powerfully as well.

Thanks for the topics, Ann!