a. the radar image was obscured (heavy rain shafts)
Although I don't know the location or the type of radar that "Tracked" QZ8501 I don't believe it possible for even heavy rain to attenuate the return from either passive or primary radar.
I have been recently posting about ADS-B data which wouldn't have come from radar. I remain puzzled by the releases of radar information re: QX8501. It seems to have been primary radar that is being referenced, not ATC radar.
I have tried to find out which primary radar might have been the one tracking the flight but I've come up to a dead end - it was apparently a naval radar that tracked the flight. I have a list of IAF radar locations but they don't seem to include the one that covered that area. A radar coverage map for Indonesia is here:
Ministry of Defense Will Add Air Force Radar
(pprune won't display just the coverage picture)
b. highly effective dislocation of the aircraft i.e. severe upward or downward displacement at a rate too swift for radar to reacquire.
Not possible.
c. in air fragmentation
This is possible but not known one way or the other. I believe it may have shed some parts.
is it true that in the modern era, no large airliners have been downed strictly by turbulence and none by lightning strikes?
I'm no historian in aviation matters but I have heard of a 707 that went down because of lightening as well as an Iranian 747.