Lee H. Marzke on 19 Jul 2017 09:12:46 -0700

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Re: [PLUG] Waaaaay Off Topic: Thunderstorm Movement

----- Original Message -----
> From: "Rich Freeman" <r-plug@thefreemanclan.net>
> To: "Philadelphia Linux User's Group Discussion List" <plug@lists.phillylinux.org>
> Sent: Tuesday, July 18, 2017 11:19:37 AM
> Subject: Re: [PLUG] Waaaaay Off Topic: Thunderstorm Movement

> On Mon, Jul 17, 2017 at 10:21 PM, Lee H. Marzke <lee@marzke.net> wrote:
>> Rich,  that is an excellent description and overview spoken like a real weather
>> junky.
> I'll take your word for that.  I know enough to be dangerous (granted,
> I'd say the same of Linux).
>> What caused you to have so much interest ?
> Well, besides my interest in the physical sciences in general I have
> an uncle who is a bit of a weather junky.  Plus, take enough
> thermodynamics and kinetics in college and it almost starts to make
> sense.
>> I'm a commercial/instrument pilot and instructor in Airplanes and also a Glider
>> instructor so weather conditions
>> are of life/death importance to me and a hobby in Gliders.
> Ah, another area where I have a lot of interest but know enough to be
> dangerous.  I tend to stick to the simulators as the sense of panic I
> tend to get when moving around in invisible air currents didn't really
> go away despite giving it a pretty fair try.  At least in an airliner
> I can just close my eyes and let somebody else land the plane if it
> gets bumpy.  The reality is that something like a Cessna 172 is pretty
> hard to lose control of, but I find that it doesn't feel that way...

The bumps don't typically bother me, except for one flight from West Chester to
Nasha NH in my Warrior  with 30K headwinds.  The Approach descent clearance into Nashua from 30NMh
out took me downwind of Mt. Monadnock and I hit the worst clear air turbulance
I've ever experienced.   It was swirling air - not bumps - causing 70 degree roll even
with full controls, and +/-20 pitch changes.   As a glider pilot - I knew Monadnock was causing it
and I was flying away from the Mt. so I knew it would get better slowing, but the
first 60 seconds I was concentrating so much on keeping the shiny side up that I
couldn't even talk.   I was then able to report the extreme turbulence to Approach and request
lower and in 5 minutes it had subsided to only severe turbulence , which felt so much better.

On the way home that night,  also with 30K winds, ATC had routed me over
the Catskill mountains, which I refused due to the likely turbulence.  I got alternate
single-engine routing directly over long island , over JFK,  then down the cost at 5000 ft.
That was really neat,  seeing all the commuters and Airliners flying on approaches
to the big airports beneath me , and I was the only single engine plane over NYC that
I heard talking that night.  Once you get the clearance  all the plains,  large and small, are
treated as part of one integrated machine.

>> The weather service routinely launches rapidly rising balloons that have
>> radiosonde packages
>> that radio back the temperature and altitude readings as they rise.  This is
>> plotted
>> as the Actual lapse rate on a Skew-T Log-P diagram.   Glider pilots use these to
>> predict expected max height of lift by taking the expected surface high
>> temperature for the day
>> and lifting a surface parcel of air at that temperature along the adiabatic
>> lapse rate on the chart until it
>> intersects the actual aloft temperatures reported from the morning soundings.
> Interesting.  In retrospect it makes perfect sense, but I had no idea
> that glider pilots bothered to use soundings.  I certainly haven't
> seen them come up in powered aviation weather.
> You seem to be describing the LCL though.  I'd expect moist air to
> rise to that level, but wouldn't it continue rising until it condensed
> out (cloud top, vs cloud base)?  Granted, you'd be inside the clouds
> at that point which you'd probably want to avoid.  Also, I don't think
> that cloud tops are so easily predicted from a sounding, unlike cloud
> base (which is why the bottoms of clouds tend to be fairly flat and
> uniform across an area compared to the tops).  So, maybe the LCL is
> all you care about, and if you manage to get above that it is just
> gravy.

With good lift the cumulus bottoms are often dark and slightly concave, and gliders
steer towards those clouds to better find good lift.  Haven't heard of the LCL. 
There is lifted-index which is also referenced.  The meteorological reports today
are greatly expanded from the 80's when I did most soaring. 

I've seen the soundings used routinely before each Regional Glider competition  (race).
They use it to determine that day's race course and length depending on predicted lift so that
fair number of contestants would be able to get back home - and not land out
in a field.  You can determine expected cloud base from the dew point.  They just
wanted to know if the race needed to be shortened or called off due to marginal lift, or
lift not high enough over the terrain to keep it safe.

Ive done cross-country glider flights - including the Silver C badge ,  but never
got to the level of competing / racing where you need to own your own high-performance
glider and fly every weekend.   My highest flight was 14,000 MSL in a 1-26 over Sugarbush VT in standing
mountain wave,  and a X/C 95M flight from Mansfield MA to Concord NH in a 1-34 ( for the Silver-c)
and 200M trip Mansfield to Concord and return in a 2-seat JanusB 40:1 fiberglass sailplane, along
with one off-airport landing in a plowed field in Framingham MA in a 1-34.   I've done nearly a thousand
glider tows in C-150 (180Hp conversion), Citabria/150Hp, and L-19 / 230Hp, which involves a
tow up to generally 3000 AGL, then steep spiral descent down after glider releases, the dropping the
tow rope beside the runway from 100Ft altitude, then sliding over the runway and landing and
taxy back to have the 200ft rope attached to both tug and glider and do it again.

In the US you can't often legally climb into the cloud in controlled airspace- so your stuck at 500ft below
cloudbase,  unless you climb up the side the cloud like I described in that frontal wave - which is very rare.

> --
> Rich
> ___________________________________________________________________________
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"Between subtle shading and the absence of light lies the nuance of iqlusion..." - Kryptos 

Lee Marzke, lee@marzke.net http://marzke.net/lee/ 
IT Consultant, VMware, VCenter, SAN storage, infrastructure, SW CM 
Philadelphia Linux Users Group         --        http://www.phillylinux.org
Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
General Discussion  --   http://lists.phillylinux.org/mailman/listinfo/plug