Atmospheric turbulence is principally represented in vertical currents and in departures from steady, horizontal flow. At jet cruising altitudes and enroute airspace, the phenomena may be induced by a number of mechanisms such as the jet stream, flow deformation, Kelvin-Helmholtz instability, orography, and gravity waves. Although there has been increased public and academic attention given to low level wind shear and upper-level clear air turbulence, relatively little research has focused on the hazard of flying outside, but in the vicinity of, convective storms. In this regard, a case study was undertaken to assist the National Transportation Safety Board investigate the cause of severe turbulence and near loss of control reported by a commercial passenger jet.
The event analyzed occurred on 12 May 1997, at approximately 1929 UTC, when an Airbus A300 enroute from Boston, MA to Miami, FL encountered severe turbulence off the coast of West Palm Beach, FL. At the time of the incident, Air Traffic Control had directed the pilot to hold at 16,000 feet because of thunderstorms and traffic near Miami International. While approaching the holding fix in seemingly benign weather conditions, the aircraft was subjected to severe turbulence, nearly stalled, and dropped over 3000 vertical feet in 30 seconds.
Miami WSR-88D base data was used to produce PLAN view and vertical cross-sections in the region between the thunderstorms and flight track. Analysis showed that at initial upset, the aircraft was separated from the periphery of the nearest thunderstorm by at least 20 km and was in a region of low reflectivity. Range Height Indicator (RHI) snapshots and animations also revealed windshears or rotors were present near flight level, before and after the incident. Since the incident occurred downstream of vertically deep and intense convection, evidence is presented to show that the aircraft turbulence may have been caused, at least in part, by some sort of convectively induced wave or rotor.
* This work was sponsored by the Federal Aviation Administration. The views expressed are those of the authors and do not reflect the official policy or position of the U.S. Government.
+ Opinions, interpretations, conclusions and recommendations
are those of the authors and are not necessarily endorsed by the United
States Air Force
The 8th Conference on Aviation, Range, and Aerospace Meteorology