Had to soak a big roasting pan for a few days to get the burned-on stuff loosened up.
When I went to wash it last night, I noticed that the globules of leftover fat were moving with the "current." The water was clearly swirling around the pan, very slowly, for no apparent reason.
It had obviously been doing it for some time, as a mass of globules had come together into in the center of the pan, and the mass was slowly rotating. The rest of the globules were arranged in a swirl pattern and were rotating with the central mass.
I let it sit for several more hours, thinking it would settle down, but it was still moving when I went back and dumped the pan.
Something was keeping the water swirling in that pan, evidently for 3 days. The pan was on the counter, next to the sink, off to the side of the kitchen window.
Have fun with this one, but some serious suggestions as to what was causing this phenomenon would be appreciated.