Traveling wave

Here's an interesting excerpt from Steve's flight on Sunday. The wind was NNW, and he took a high tow, looking for wave. The excerpt begins at A. The flight path is colored according to the variometer reading (blue is down and orange is up). After a left turn in sink, he runs into lift while headed south (downwind). At point B he turns around and makes a series of S-turns back into the wind, climbing all the way in smooth air. It quits at C, so he does another reversal and flies precisely back the way he came. This time, there's no lift. He climbed 500 feet in smooth air, but when he returned to the same spot, the lift wasn't there.

There were no thermals that day, and it was too smooth to be rotor lift. I think that this is an example of a "traveling wave," a ripple in the atmosphere that isn't stationary.