Near Denver on July 11 1988, a moderate-reflectivity thunder-storm produced a microburst of unusual intensity during the test operation of the Terminal Doppler Weather Radar (TDWR) system. This microburst-producing storm, unlike those previously investigated, contained a complex updraft structure and an intense microburst downstream from the main precipitation shaft. Of special significance is that several successive airliners inadvertently encountered the microburst during final approach to Stapleton Airport. This paper focuses on the numerical investigation of this storm - via simulation with the Terminal Area Simulation System (TASS). Evolution and structure of the storm, including hazard indices based on F-factor, are presented and compared with "observed" data, including that measured by Doppler radar and aircraft flight data recorders. Model results show that multiple low- to moderate-reflectivity microbursts formed downshear of the main precipitation shaft. The most intense of the modeled microbursts contained a velocity differential exceeding 40 m/s, strong downdrafts, and hazardous windshear with F-factors approaching 0.2. Outflow from this microburst was roughly symmetric at ground level during peak intensity, but became more asymmetric with time and altitude above the ground. The intense microburst, not unlike the real microburst that was encountered by the aircraft, originated from light precipitation that was swept downwind of the primary source. In contrast to the intense microburst, downdrafts and outflows associated with the simulated storm's main precipitation shaft were less vigorous by comparison, even though accompanied by higher magnitudes of radar reflectivity. Additional simulations with the axisymmetric version of TASS configured from the 3-D simulation, suggest that the intense microburst was driven by cooling primarily from sublimating snow.
