Originally Posted by
ATC Watcher
As to the vertical speed , it is very unreliable due accuracy of mode S (25 ft variations) it is common that short variations, especially in turbulence can send messages with 10.000ft VS. This is most probably why we see 30.000ft on the ADS-B diagram posted earlier. I would think it might be a brief acceleration, but not a continuous descent at that rate.
Yes, the VRate parameter of ADS-B is very unreliable for the reasons you state, but sadly it's clear simply from the altitude profile of the last recorded 15 seconds or so of the flight that the ROD would have been well into 5 figures.