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Posted by Ray
on 4/10/2012, 8:42 pm, in reply to "Re: Where to find "dry adiabats""
74.65.47.166
Well one way is to read and study the Buffalo NWS discussion:
http://www.erh.noaa.gov/displayprod.php?product=BUFAFDBUF&versions=10
These discussions are a little technical, but should be NBD for most pilots. Note that they change frequently: when models change their minds, so do us forecasters. For example: this one, 12 hours after this morning's, casts doubt that the residual moisture on Thursday morning will be gone by noon. When trying to nail down clearing time, a good tool is the 500/700 mb vertical motion prog (negative means sinking, warming, and clearing), along with the 850/925 mixing ratio (moisture) progs:
http://weather.rap.ucar.edu/model/displayMod.php?var=eta_4_vertvel&loop=1
If you advance thru the loop to the 48 hr panels (as I type this at 9:31 PM EDT), "valid" for 1200 UTC Thursday (7 AM EDT), you still see sinking and relatively dry air. But the magnitude of the sinking is small...if it goes even a little positive, the clouds will stay all day. We'll have a better handle on this tomorrow afternoon...will tweak Thursday's outlook then.
--Previous Message--
: Where do we find the forecast for: today,
: tomorrow, etc?
:
: --Previous Message--
: Good question. I have a pile of met books
: that
: you don't, so: I Googled "dry adiabatic
: lapse rate"...and got 125,000 hits! I
: read thru a bunch. Wikipedia's is
: good...contains a bunch of math which you
: can skip, just read the words and get a lot
: out of it. But, you need a good
: understanding of what "adiabatic"
: really means in the first place. Here is the
: site I recommend for starters...then you can
: go math crazy on the other sites if you
: wish:
:
:
:
: http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/atmospheric_moisture/lapse_rates_1.html
:
: --Previous Message--
: Is there a site that we can get to?
:
: --Previous Message--
: 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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