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)