For the record there have been a number of Boeing's lost in turbulence/thunderstorms.
Northwest 720 out of Miami Feb 12, 1963, although the tail wasn't the first to go. The aircraft broke up when the pilots started to regain control. Aircraft had flown into a violent turbulence associated with a thunderstorm line.
BOAC 707-436 March 6 1966: Tail was hit by a mountain wave off Fuji on a sightseeing diversion as weather was "perfect". The aircraft was from Tokyo to HK and captain requested ATC clearance to descend to about level with the top of Fuji. Tail collapsed to the left and took with it the horizontal stabilizer on that side, which cause a violet pitch motion that took all engines off. Front broke off in the descent.
A BAC1-11 of Braniff was also lost to thunderstorm in August 1966. The aircraft was struck by violent turbulence ahead of a thrunderstrom line in clear air.
The strong shear struck from the rear and took out the elevators and rudder, although the basic tail stayed intact initially. Stardboard wing then failed.
Geoffrey Thomas