History of Flight: On July 15, 2010, at about 0200 UTC, a Boeing 767-332ER, registered in the United States as N184DN and operated by Delta Airlines, encountered turbulence at flight level 360 near TOESS intersection north of Antonio B. Won Pat International Airport (GUM) Guam. One flight attendant suffered a broken ankle during the turbulence event. The flight had departed GUM at 1125 UTC and landed at Narita International Airport (NRT), its original destination, at 0344 UTC. None of the other 192 passengers or 9 crewmembers were injured. The flight was operating under the provisions of 14 Code of Federal Regulations (CFR) Part 121, and was on an instrument flight rules flight plan, and flying in visual meteorological conditions at the time of the event. According to the captain of the flight, at the time of the turbulence encounter he was navigating around scattered cloud build-ups. Nothing was showing on radar, as he adjusted the antenna tilt between -1 and -5 degrees. At that time the seatbelt sign was not illuminated. According to the injured flight attendant, she was walking down the aisle between the mid galley and the aft galley and fell to the floor at the time of the turbulence encounter. Injuries: None of the other 9 crewmembers or the 192 passengers were injured. Damage to Airplane: The airplane was not damaged. Meteorological Information: According to the operator, no turbulence was forecast for the area in which the airplane was flying at the time of the turbulence encounter. In addition, satellite imagery revealed that the airplane was in an area not conducive to turbulence when the event occurred. Medical and Pathological Information: The injured flight attendant was examined by a physician passenger who did not provide a diagnosis. She declined medical treatment upon arrival at Narita and proceeded to her home base of Minneapolis before seeking further medical advice. Upon arrival home, she saw a doctor who stated that her ankle was broken. Flight Data Recorder: According to the flight data recorder, the vertical acceleration during the turbulence encounter varied between +1.5 g and -0.3 g. The encounter lasted about 5 seconds.