Commercial Aircraft Encounters with Thunderstorms in the Memphis Terminal Airspace

Obtaining a quantitative understanding of pilot decision-making in convective weather avoidance situations is essential for the design of effective terminal weather products, air traffic management systems, and for improving safety. Rhoda and Pawlak (1999) found that the thunderstorm penetration and deviation behavior of commercial airline pilots in the Dallas/Fort Worth (DFW) airspace was strongly correlated with precipitation intensity, geographic coverage of precipitation, and range from the destination airport. They found that vertically integrated liquid water (VIL) was more closely correlated to pilots' behavior than a composite reflectivity product or the ASR-9 precipitation product. They also showed that, contrary to stated industry practice, pilots frequently penetrated heavy precipitation near the destination airport and that they were more likely to penetrate intense storms when they 1) were following another aircraft, 2) were flying after dark, 3) had been delayed by 15+ minutes during the current leg of flight.

This paper describes a companion study to Rhoda & Pawlak's DFW study. Weather and flight track data were collected and examined for 15 convective weather days in the Memphis terminal airspace. Aircraft encounters with thunderstorms were identified and divided into penetrations and deviations. Weather variables were extracted from NEXRAD, TDWR, ASR-9, and lightning data for each thunderstorm encounter. The weather and flight track variables were tested for their correlation with the pilots' penetration and deviation behavior. The statistical classifiers that were developed in the DFW study were applied to Memphis data and were evaluated for their ability to predict which encounters would result in deviations.

This paper will identify the weather variables that were most strongly correlated to penetration and deviation behavior in the Memphis airspace and will compare the Memphis and Dallas results. The Memphis study extends the Dallas study in several important aspects: 1) it examines weather avoidance by departing aircraft, 2) it compares the behavior of package-delivery carrier pilots with that of passenger-carrier pilots, and 3) it provides an opportunity to compare the impact of overall airport traffic loads (e.g. an airport with continual high volume flows [DFW] versus one with less frequent high traffic periods [MEM]).