What happened
On November 26, 2012, a Japan Airlines Boeing 767-300, registered JA610J, was operating flight 877 from Narita International Airport to Shanghai Pudong International Airport. The flight was carrying 171 people, including 159 passengers and 12 crew members.
While cruising at 36,000 feet over Fujinomiya City, Shizuoka Prefecture, the aircraft encountered sudden and severe turbulence. Digital flight data recorder (DFDR) records indicated significant vertical acceleration changes, fluctuating between +1.9 G and +0.7 G within a single second. At the time of the event, the seatbelt sign had been turned off, and several passengers were moving through the cabin. One passenger, who was walking near the aft lavatories, lost his balance during the intense shaking, resulting in a fractured right ankle. The aircraft eventually landed safely in Shanghai, where the injured passenger was transported to a hospital.
The investigation
The Japan Transport Safety Board (JTSB) examined flight data, meteorological satellite imagery, and atmospheric charts to determine the cause of the turbulence. Investigators analyzed infrared imagery which showed a "Transverse Band" and a "Bulge" moving through the region, as well as hourly analysis charts to identify vertical wind shear (VWS) patterns. The investigation also reviewed the pilot's actions, noting that the crew had previously identified potential weather risks and had planned a descent to avoid known disturbances, yet the specific pocket of turbulence was not detected by the on-board weather radar or reported by other aircraft in the vicinity.