447 entered an updraft, it is on record. after exerting its influence on her, she started to climb, and reached a VS of 500fpm. What was the velocity of the updraft? 500fpm? Hardly. let's be conservative and call it 60 knots, vertical. Before the airframe rises, the pitots are sampling the airflow. If 60 knots on the nose, the IAS is 60 knots increased. If on the tail, 60 knots reduced. How about straight up? 30 knots less, and sampled simultaneously by all three probes. This is enough to cause the a/c to reject NORMAL LAW, and degrade to ALTERNATE. It also explains some Mach deviations reported in the DFDR. After sufficient time to outwait a possible anomalous loss of AS, the A/P is commanded to quit, after the RTLU locks.
Now this does not solve the problem of what happened, but it does suggest that perhaps an obsession with ICE may want a look. It may also call to question the reliance on this autoflight system in a cell.