Yet another potential source of lift?

http://science.nasa.gov/headlines/y2007/11oct_undularbore.htm?list812469

The question is how long do they last and how far they propagate?
And, of course, how do you catch one?

-Tom

And, how fast do the propagate? Looks pretty fast to me - horizon to
horizon in 5 minutes at >10k ft?


On Oct 11, 9:53 pm, 5Z > wrote:
> Yet another potential source of lift?
>
> http://science.nasa.gov/headlines/y2007/11oct_undularbore.htm?list812469
>
> The question is how long do they last and how far they propagate?
> And, of course, how do you catch one?
>
> -Tom

On Oct 11, 10:53 pm, Sarah > wrote:
> And, how fast do the propagate? Looks pretty fast to me - horizon to
> horizon in 5 minutes at >10k ft?
>
> On Oct 11, 9:53 pm, 5Z > wrote:
>
> > Yet another potential source of lift?
>
> >http://science.nasa.gov/headlines/y2007/11oct_undularbore.htm?list812469
>
> > The question is how long do they last and how far they propagate?
> > And, of course, how do you catch one?
>
> > -Tom

i was at work that day but matt michael (wby0nder) called me to tell
me of these incredible waves which he was sure were soarable and were
even visible on radar. they seemed to stretch clear across the state,
seemed to me that you could just shoot to the northeast as fast as
your little glider could go. maybe i could do 1000 km in the
Cherokee :D:D

On Oct 11, 9:53 pm, 5Z > wrote:
> Yet another potential source of lift?
>
> http://science.nasa.gov/headlines/y2007/11oct_undularbore.htm?list812469
>
> The question is how long do they last and how far they propagate?
> And, of course, how do you catch one?
>
> -Tom

I live about 30 miles north of Des Moines and observed this with
interest. I immediately sent out an email to the Cherokee Kid (Tony
Condon) who lives 100 miles east of me in case it held together long
enough for him to see it too.

"Tony,
A couple of morning glory type roll clouds just swept past our place
heading east. They are outflow from the storms just west of us. My
camera was dead unfortunately. You could clearly see the inflow lift
on the leading edge. I could see at least 20 miles north and south
along the clouds so they were at least that long. If you go to DSM
NWS radar base loop you can see it pretty clearly
http://radar.weather.gov/radar.php?rid=DMX&product=N0R&overlay=11101111&loop=yes

Quite soarable in my estimation"


After observing the radar loop for some time I added this note:

"Based on the radar signature it's moving about 40 mph to the
southeast and currently extends from about Rhodes to New Virginia or
about 60 miles in length. Could easily be longer just not showing up
on the scan. There are both a primary and secondary visible on the
radar and I saw 2 from here roughly 3 miles apart."

I'd roughly estimate that the cloud base was 1500 to 3000 feet AGL and
the top of the primary was 3 to 5k AGL. I think that soaring it would
have been quite straightforward, a combination of wave and ridge
technique with emphasis on staying in the clear ahead of the wave.
Tony replied with concern about having to land in high winds and/or
thunderstorms to which I replied...

"Actually, in many cases, including this one, the outflow boundary out-
races the storms by a considerable margin. The last radar scan that
still shows the boundary paints it from near Grinnel to Osceola and
apparently slowing down. It's about 20 miles ahead of the precip
echos which by the way are pretty darn tame anyway. The highest winds
in the whole thing occured around the wave itself and they were only
in the low 20kts at best judging by conditions at passage here."

It might have been a trick to convince a tow pilot to launch with
T'storms lurking a few miles west and the timing would have to be
precise. Based on the inflow condensation I bet the lift was
fantastic on the leading edge. The nice thing is that unlike the AU
Morning Glory you can land almost anywhere around here for hundreds of
miles. However, these are not as predictable though I believe as
common as the meteorologist says in the link commentary. I've seen
this many times over the years, sometimes way too close to storms but
other times plenty far away. Sometimes the waves continue for hours
after the storms completely dissapate. In this case a couple of small
precip echos appeared to be generated by the waves passage. They were
not too huge or persistant and I believe could have been navigated/
avoided by a watchful prudent glider pilot. Sometimes these grow into
monster tornadic thunderstorms which you would not want to be anywhere
near in a sailplane. Determining when to latch on to one of these
waves could be a tricky judgement call.

Matt Michael
Ames Iowa

wrote:
> Sometimes these grow into
>monster tornadic thunderstorms which you would not want to be anywhere
>near in a sailplane. Determining when to latch on to one of these
>waves could be a tricky judgement call.
>
>Matt Michael
>Ames Iowa

Pretty cool stuff but....Yeeeesh.

to quote the Nasa comments:

"Furthermore," he says, "undular bores may be a source of thunderstorms."
That's right, thunderstorms make undular bores and undular bores return the
favor. "These waves churn up the atmosphere, causing instabilities that can
initiate and sustain severe storms."
For one thing, we believe undular bores can amplify tornadoes." He cites as
an example an F5 tornado that struck the outskirts of Birmingham, Alabama, in
April 1998."

I rode the approaching wall of a cu-nim at about 10mi. here in California
once. I thought I was keeping ahead of the bugger but it was like the sky
around me jus' suddenly started blowing up while the cell itself seemed to
still be a way off. It was like the mass of the T-head was pushing activity
way ahead.

I just don't mess with that stuff anymore.

Let us know how it goes for ya should you contact one of these. Looks really
interesting.

--
Message posted via http://www.aviationkb.com

Another new phenomenon for glider pilots to explore.
I note that they may be more common at night. I wonder how feasible a night=
-rating for gliding might be.
It would take the challenge to a whole new level, especially as most instru=
ment panels, glider sites, hillsides and fields are unlit.
=20
Rory
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