In 30 years of flying, including the Bay of Bengal, clear air always the worst!
1. B707 500 miles off Newfoundland in severe turbulence, two galleys broke loose, pax and crew injured, then the yaw damper failed, rolling to 40 degrees of bank, had to make an emergency descent. How the aircraft stayed together I will never know.
2. B707 over North Africa in severe turbulence all the flight instruments failed...bar the standbys...no idea what mach we were doing...em desc into smoother air. Turns out from the flt recorder we descended at .94 mach! (seemed a bit noisy).
3. B737-200 just north of the Alps, heading north, NW jetstream of 150kts. In mod/sev turb aircraft, was descending at 1500fpm instead of climbing at 800fpm, to maintain speed. A following company a/c had 2 cc injured, one with a broken ankle, the other with a compressed vertibrae.
Weather or Ts turbulence is mostly finite, and avoidable, and you know when it will end! Clear air can be so unpredictable as to duration and severity. Turbulence on an approach is where the skill and judgement comes in...the fun bit!