What happened
While operating at 31,000 feet in night visual meteorological conditions, an MD-82 encountered turbulence in the vicinity of Charlotte, North and Carolina. The flight had been smooth with occasional light chop, and the seat belt sign was turned off. At the time of the incident, approximately seven people were standing in the cabin, including three flight attendants.
At approximately 2207, the aircraft entered instrument meteorological conditions and encountered moderate chop followed by a very sharp jolt. The captain immediately activated the fasten seatbelt sign after the first jolt, after which the aircraft experienced two additional sharp jolts. During this period, rain and St. Elmo's fire were present. The captain turned the aircraft to the right, heading back toward previously visible ground lights, and notified FAA Air Traffic Control Jacksonville Center of the maneuver and the turbulence. Within approximately 30 seconds, the flight returned to visual meteorological conditions with only light chop remaining.
The encounter resulted in one passenger receiving serious injuries.
The investigation
The NTSB examined radar and weather data related to the flight. When the aircraft's flight path was overlaid with infrared satellite imagery, an isolated thunderstorm with cloud tops reaching approximately 36,000 feet was identified near the GLOVR intersection at 2145. Subsequent data from 2202 and 2215 indicated that the thunderstorm had expanded and moved northeast along the aircraft's track, with cloud tops increasing in height.
Digital Doppler weather radar data from Greer, South Carolina, showed reflectivity echoes at the location of the turbulence, ranging from very light to intense. Radar cross sections indicated the flight penetrated areas with maximum radar tops of approximately 40,000 feet. An examination of the aircraft's Flight Data Recorder confirmed altitude changes and fluctuations in vertical and lateral acceleration consistent with the reported event.