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Posted by Ray
on 4/10/2012, 4:27 pm, in reply to "Re: Weather Courtesies"
74.65.47.166
David: yes, of course, would love to. Weather is so hugely complex that we are all "newbies", why thousands of man-years of study and computer modeling still can't reliably predict anything beyond a few days. It's impossible to pitch any talk at a level encompassing everyone, but...our club is chock full of gifted and talented individuals who are not intimidated by the sight of a double or contour integral. And one can get across some rather sophisticated concepts without using those. An hour lecture on fluid mechanics and thermodynamics as applied to the atmosphere is a lot to swallow in one gulp. What I've been doing (and will continue to, as in next paragraph) is occasionally throwing out a non-trivial tidbit or teaser on the Message Board, then people who want to learn more can Google the technical term I may have used.
Skew T? Congratulations, you have zeroed in on one of the most important tools of all, the one all serious forecasters always look at. Although, I wish NWS had ditched this particular plot format decades ago, but it is so firmly entrenched you can't get rid of it. Why? Because you have to compare the lapse rate to various slanted reference lines, the most important of which for the soaring pilot are the dry adiabats. Because a dry adiabat is what a thermal follows (well, almost). I used to have, of the three monitors on my old workstation, one of them with a different aspect ratio display compared to the others...drove you nuts when trying to compare several simultaneously-displayed soundings. Here's where introducing a more complicated variable actually makes things transparently simple. That variable is potential temperature...that remains constant when a thermal goes up, or you mechanically and violently stir up the air, as severe wind shear and rotor can do. So, on a plot of potential temperature versus height, you can see instantly what kind of a day you're in for, 'cause the dry adiabats are always vertical lines, regardless of whether plotted against height, log height, or whatever. When the lines slant forward with height (as in forward slash), the air is stable any you ain't goin' anywhere. The lines usually only slant backward with height in the shallow (few meters deep) "super-adiabatic" layer near the ground, and cause shimmering and water mirages over the desert. But sometimes they slant backwards for thousands of feet...that's when Dorothy starts asking if she's still in Kansas.
http://en.wikipedia.org/wiki/Potential_temperature
--Previous Message--
: Ray;
:
: It might be helpful if you could give a
: ground school at some point to initiate us
: newbies.
:
: I've spent some time trying to learn about
: the SkewT plots but there is a lot to
: digest.
:
: Maybe later in the day during soarfest?
:
: David
: --Previous Message--
: March, when we weren't ready, was most
: courteous. So far in April, Mother Nature
: has been getting even. Although, anyone
: looking at the sky yesterday, which featured
: 7 - 8 K cloud bases and enough wind to mount
: a challenge to Kai's NY state distance
: record...if you could have gotten launched
: early enough to be safe...knows things are
: improving.
:
: WARNING : from time to time, and especially
: when unusually interesting scenarios are
: developing, these discussions may get a bit
: technical. If terms like "entropy"
: and "quasi-geostrophic flow" are
: not your cup of tea, save yourself both time
: and an unhealthy increase in blood pressure
: by just skipping it, no one's forcing you to
: read it. There are some in the club
: interested in learning more than what is
: provided by Aviation Weather or Flight
: Service...and those are the target of such
: discussions.
:
: For a healthy increase in blood pressure, as
: in happy excitement, Nature provides that
: later this week. After the next little nasty
: during mid week (snow?), the latter part is
: looking great. Thursday is definitely the
: stronger XC distance day, in honor of Alex's
: birthday. There may be morning clouds from
: residual moisture, especially over Rochester
: downstream from warm (for this time of year)
: Lake Ontario...but they will erode quickly.
: If you wait for the sun before going to the
: airport, you'll miss your chance for Gold
: distance, or even Diamond if it weren't for
: the airspace strictures in place on the
: Delmarva since 911.
:
: Friday is going to be another winner...no
: morning overcast to worry about...and the
: better day for triangles and other tasks
: ending at DSV. How high cloud base? You
: need to check the morning sounding.
:
: By the weekend, the models diverge
: significantly and disturbingly. Stay tuned.
:
: So there, I avoided any "big
: words"!
:
:
:
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