A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Soaring
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

for the amateur meteorologists, question.



 
 
Thread Tools Display Modes
  #1  
Old October 19th 20, 08:22 PM posted to rec.aviation.soaring
john firth
external usenet poster
 
Posts: 127
Default for the amateur meteorologists, question.


Maybe the last flight of the year, but memorable.

Atmosphere 10C, very unstable , with cloudbase 5000ft and tops above 10K; showers, wind W 15kt @ 1000ft.

climbed to 4000 (airspace limit) over the airfield ; flew upwind along a cloud street, holding 4000ft.
Street ended after 10 miles , then strong sink for 5 miles ending under a large cu.; at 1200 AGL
found zero sink but little more. Started circling but losing slowly, expecting to find real lift,
but probing found nothing better. Considered starting the engine, but that is admitting defeat too
early, with good fields below; and so I circled in smooth air and drifted, gaining 100 and losing it.
Clouds 4000 ft above drifted past.
Have faith! Unstable air has to get it together and accelerate; the fields drifted steadily
by underneath, in the weak October sunshine, interspersed with large woods, .
This went on for a long time, round and round, airfield unreachable even downwind.
( would I ever contemplate a 15 kt downwind landing? only as a life saver)
and so after 40 mins, still at about 1000 AGL, I see a dual lane highway, the airfield a mile beyond.
surprise! I can reach the airfield; after another couple of circles, I abandon the "thermal" and immediately hit 2 kts. End of suspense. I had drifted 14 miles at 1000ft in 50 mins doing 120 circles.

Now for the question: how does a parcel of air over 600ft diameter maintain a steady ascent
of 150 fpm for nearly an hour without either breaking away or dissipating. This was not a donut
as there was no central core. It must have been replenished from below.

Any similar experiences?

Have a well socially distanced winter!

John Firth (PIK 20E)
  #2  
Old October 19th 20, 09:30 PM posted to rec.aviation.soaring
John Foster
external usenet poster
 
Posts: 354
Default for the amateur meteorologists, question.

On Monday, October 19, 2020 at 1:22:11 PM UTC-6, john firth wrote:
Maybe the last flight of the year, but memorable.

Atmosphere 10C, very unstable , with cloudbase 5000ft and tops above 10K; showers, wind W 15kt @ 1000ft.

climbed to 4000 (airspace limit) over the airfield ; flew upwind along a cloud street, holding 4000ft.
Street ended after 10 miles , then strong sink for 5 miles ending under a large cu.; at 1200 AGL
found zero sink but little more. Started circling but losing slowly, expecting to find real lift,
but probing found nothing better. Considered starting the engine, but that is admitting defeat too
early, with good fields below; and so I circled in smooth air and drifted, gaining 100 and losing it.
Clouds 4000 ft above drifted past.
Have faith! Unstable air has to get it together and accelerate; the fields drifted steadily
by underneath, in the weak October sunshine, interspersed with large woods, .
This went on for a long time, round and round, airfield unreachable even downwind.
( would I ever contemplate a 15 kt downwind landing? only as a life saver)
and so after 40 mins, still at about 1000 AGL, I see a dual lane highway, the airfield a mile beyond.
surprise! I can reach the airfield; after another couple of circles, I abandon the "thermal" and immediately hit 2 kts. End of suspense. I had drifted 14 miles at 1000ft in 50 mins doing 120 circles.

Now for the question: how does a parcel of air over 600ft diameter maintain a steady ascent
of 150 fpm for nearly an hour without either breaking away or dissipating. This was not a donut
as there was no central core. It must have been replenished from below.

Any similar experiences?

Have a well socially distanced winter!

John Firth (PIK 20E)

Could it have been a line of convergence?
  #3  
Old October 20th 20, 12:58 AM posted to rec.aviation.soaring
Waveguru
external usenet poster
 
Posts: 178
Default for the amateur meteorologists, question.

Or some kind of traveling wave?

Boggs

  #4  
Old October 20th 20, 01:33 AM posted to rec.aviation.soaring
2G
external usenet poster
 
Posts: 1,439
Default for the amateur meteorologists, question.

On Monday, October 19, 2020 at 1:30:41 PM UTC-7, John Foster wrote:
On Monday, October 19, 2020 at 1:22:11 PM UTC-6, john firth wrote:
Maybe the last flight of the year, but memorable.

Atmosphere 10C, very unstable , with cloudbase 5000ft and tops above 10K; showers, wind W 15kt @ 1000ft.

climbed to 4000 (airspace limit) over the airfield ; flew upwind along a cloud street, holding 4000ft.
Street ended after 10 miles , then strong sink for 5 miles ending under a large cu.; at 1200 AGL
found zero sink but little more. Started circling but losing slowly, expecting to find real lift,
but probing found nothing better. Considered starting the engine, but that is admitting defeat too
early, with good fields below; and so I circled in smooth air and drifted, gaining 100 and losing it.
Clouds 4000 ft above drifted past.
Have faith! Unstable air has to get it together and accelerate; the fields drifted steadily
by underneath, in the weak October sunshine, interspersed with large woods, .
This went on for a long time, round and round, airfield unreachable even downwind.
( would I ever contemplate a 15 kt downwind landing? only as a life saver)
and so after 40 mins, still at about 1000 AGL, I see a dual lane highway, the airfield a mile beyond.
surprise! I can reach the airfield; after another couple of circles, I abandon the "thermal" and immediately hit 2 kts. End of suspense. I had drifted 14 miles at 1000ft in 50 mins doing 120 circles.

Now for the question: how does a parcel of air over 600ft diameter maintain a steady ascent
of 150 fpm for nearly an hour without either breaking away or dissipating. This was not a donut
as there was no central core. It must have been replenished from below.

Any similar experiences?

Have a well socially distanced winter!

John Firth (PIK 20E)

Could it have been a line of convergence?


https://chessintheair.com/convergence/
  #5  
Old October 20th 20, 02:41 AM posted to rec.aviation.soaring
Martin Gregorie[_6_]
external usenet poster
 
Posts: 699
Default for the amateur meteorologists, question.

On Mon, 19 Oct 2020 12:22:08 -0700, john firth wrote:

Maybe the last flight of the year, but memorable.

Atmosphere 10C, very unstable , with cloudbase 5000ft and tops above
10K; showers, wind W 15kt @ 1000ft.

climbed to 4000 (airspace limit) over the airfield ; flew upwind along
a cloud street, holding 4000ft. Street ended after 10 miles , then
strong sink for 5 miles ending under a large cu.; at 1200 AGL found zero
sink but little more. Started circling but losing slowly, expecting to
find real lift,
but probing found nothing better. Considered starting the engine, but
that is admitting defeat too early, with good fields below; and so I
circled in smooth air and drifted, gaining 100 and losing it. Clouds
4000 ft above drifted past.
Have faith! Unstable air has to get it together and accelerate; the
fields drifted steadily by underneath, in the weak October sunshine,
interspersed with large woods, .
This went on for a long time, round and round, airfield unreachable
even downwind.
( would I ever contemplate a 15 kt downwind landing? only as a life
saver)
and so after 40 mins, still at about 1000 AGL, I see a dual lane
highway, the airfield a mile beyond.
surprise! I can reach the airfield; after another couple of circles, I
abandon the "thermal" and immediately hit 2 kts. End of suspense. I
had drifted 14 miles at 1000ft in 50 mins doing 120 circles.

Now for the question: how does a parcel of air over 600ft diameter
maintain a steady ascent of 150 fpm for nearly an hour without either
breaking away or dissipating. This was not a donut as there was no
central core. It must have been replenished from below.

Any similar experiences?

Yep, but not recently.

This was definitely convergence over the front of sea-air incursion. A
winch launch at Gransden Lodge, 10 miles west of Cambridge UK, put me in
zero sink with a cloud line, which turned out to be a convergence line,
running N-S along the road about 1 km to the east. I cruised over to it
with no height loss, turned north along it cruising at 50 kts and
climbing slowly but steadily to cloud base at 3500/4000 ft. It ended
around 5miles/8km I glided out to the motel on the A1 at Peterborough and
back to the cloud line for the loss of around 1500ft, drove back along it
to GRL and landed. That was my first XC in my 201 Libelle - a 100km out
and return in almost exactly an hour.

I haven't seen convergences like that in the last few years, but they
used to be frequent enough not to be unusual in Eastern UK and were
almost always in calm, high pressure conditions when an E or NE breeze
brought sea in from the North Sea.


--
Martin | martin at
Gregorie | gregorie dot org

  #6  
Old October 21st 20, 06:57 PM posted to rec.aviation.soaring
john firth
external usenet poster
 
Posts: 127
Default for the amateur meteorologists, question.

On Monday, October 19, 2020 at 11:41:14 PM UTC-2, Martin Gregorie wrote:
On Mon, 19 Oct 2020 12:22:08 -0700, john firth wrote:

Maybe the last flight of the year, but memorable.

Atmosphere 10C, very unstable , with cloudbase 5000ft and tops above
10K; showers, wind W 15kt @ 1000ft.

climbed to 4000 (airspace limit) over the airfield ; flew upwind along
a cloud street, holding 4000ft. Street ended after 10 miles , then
strong sink for 5 miles ending under a large cu.; at 1200 AGL found zero
sink but little more. Started circling but losing slowly, expecting to
find real lift,
but probing found nothing better. Considered starting the engine, but
that is admitting defeat too early, with good fields below; and so I
circled in smooth air and drifted, gaining 100 and losing it. Clouds
4000 ft above drifted past.
Have faith! Unstable air has to get it together and accelerate; the
fields drifted steadily by underneath, in the weak October sunshine,
interspersed with large woods, .
This went on for a long time, round and round, airfield unreachable
even downwind.
( would I ever contemplate a 15 kt downwind landing? only as a life
saver)
and so after 40 mins, still at about 1000 AGL, I see a dual lane
highway, the airfield a mile beyond.
surprise! I can reach the airfield; after another couple of circles, I
abandon the "thermal" and immediately hit 2 kts. End of suspense. I
had drifted 14 miles at 1000ft in 50 mins doing 120 circles.

Now for the question: how does a parcel of air over 600ft diameter
maintain a steady ascent of 150 fpm for nearly an hour without either
breaking away or dissipating. This was not a donut as there was no
central core. It must have been replenished from below.

Any similar experiences?

Yep, but not recently.

This was definitely convergence over the front of sea-air incursion. A
winch launch at Gransden Lodge, 10 miles west of Cambridge UK, put me in
zero sink with a cloud line, which turned out to be a convergence line,
running N-S along the road about 1 km to the east. I cruised over to it
with no height loss, turned north along it cruising at 50 kts and
climbing slowly but steadily to cloud base at 3500/4000 ft. It ended
around 5miles/8km I glided out to the motel on the A1 at Peterborough and
back to the cloud line for the loss of around 1500ft, drove back along it
to GRL and landed. That was my first XC in my 201 Libelle - a 100km out
and return in almost exactly an hour.

I haven't seen convergences like that in the last few years, but they
used to be frequent enough not to be unusual in Eastern UK and were
almost always in calm, high pressure conditions when an E or NE breeze
brought sea in from the North Sea.


--
Martin | martin at
Gregorie | gregorie dot org


I am afraid none of these ideas fit the observations; I am familiar with convergence
lines ( this was not a line) both as a lake effect and locally, terrain differential.
waves are not stable in a unstable atmosphere nor is the flat , slightly ridged terrain
condusive to wave generation.
The puzzle is that this bubble did not coalesce with a convective cloud passing overhead.

John F
  #7  
Old October 21st 20, 10:46 PM posted to rec.aviation.soaring
WaltWX[_2_]
external usenet poster
 
Posts: 310
Default for the amateur meteorologists, question.

John,

Likely the answer is some kind of weak linear region of lift or convergence.. The atmospheric boundary layer if one could look down it often has lift lines parallel to the wind... or the lines look like like a "mesh" pattern. These may not be referenced necessarily to terrain or ground features.

Walt Rogers WX


  #8  
Old October 22nd 20, 01:41 AM posted to rec.aviation.soaring
Waveguru
external usenet poster
 
Posts: 178
Default for the amateur meteorologists, question.

Waves aren't always generated by hills or mountains, sometimes the air bounces off of another air mass.

Boggs
  #9  
Old October 22nd 20, 03:38 AM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 774
Default for the amateur meteorologists, question.

Basically, we don't understand meteorological conditions on the micro-micro level, as in the anomalies that happen for whatever reason in a tiny area. Of course, the "tiny" area is much smaller than can be predicted from satellite imagery, atmospheric analysis of airmass movement and surface disturbances. Essentially it all boils down to just flying in it and making some guesses about what is happening. The best competition pilots generally have many hours and good memories, enough so that they can recognize conditions they have experienced in the past and make assumptions and decisions based on prior knowledge.

For the rest of us, we are essentially clueless until someone with more data can provide a reasonable explanation. And even then, there is a good chance they are blowing smoke. Remember that it was less than 100 years ago (1933) that mountain wave formation was observed and explored by Wolf Hirth and Hans Deutschmann.

Trying to explain atmospheric phenomena requires lots of data, gathered a few bits at a time, and needs to be experienced by as many observers as possible to build even a little bit of understanding.

We used to say in hang gliding, "If we could see air, we'd probably quit flying!"
  #10  
Old October 22nd 20, 07:32 AM posted to rec.aviation.soaring
krasw
external usenet poster
 
Posts: 668
Default for the amateur meteorologists, question.

On Thursday, 22 October 2020 at 03:41:13 UTC+3, Waveguru wrote:
Waves aren't always generated by hills or mountains, sometimes the air bounces off of another air mass.

Boggs


Waves form in stable layer, convection in neutral layer. Hard to imagine you could connect with wave 1000ft agl and same time have cu clouds passing above.
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Amateur Built - Spacecraft? Richard[_8_] Home Built 2 June 20th 12 09:03 PM
Amateur Emerald Glenn[_2_] Aviation Photos 0 July 27th 07 03:24 PM
Amateur night at the field Viperdoc Piloting 33 May 13th 06 06:28 PM
Amateur Question: Meaning of "Heavy" Robin General Aviation 3 September 1st 04 05:12 AM
amateur design consultant? Shin Gou Home Built 14 June 30th 04 01:34 AM


All times are GMT +1. The time now is 12:51 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.