infrequent flyer 789.
The a/c was NOSE DOWN at handoff. It was also climbing at 1000fpm. So, yeah, VS. Robust UPDRAFT. I don't pretend to know what each pilot saw, but it seems that one was using ATT the other VS. At least at first. Then, perhaps each one, feeling 'burned' by one or the other of the instrument readings, switched horses.
Never the twain to meet. Frankly, in the longer term, the PNF had the better guess. It is clear from the absolute gitgo that the pilots were not flying the aircraft as most experts on this thread would have. But they were not up to the standard evident here, alas.
The ship was climbing 1000fpm. What does that say about the Zipper? With the turbulence ("fortes"), I still am not convinced ICE was the culprit re: speeds.