Those who would take Archie Trammell as gospel should be made aware that while he was doing a service, he was selling his services, so was not unbiased.
Flt 191 Delta 1011 had the old Arinc 564 radar with all its sidelobes and other limitations. The Bendix and Collins Arinc 700 digital wx radars had been in operation three years already in the 767, 757 and other airplanes. Those radars were designed to overcome the limitations of the prior radars, around which Trammell's course was built. The new radars provide(d) a reliable solution to shadowing: Path Attenuation Compensation, and PAC Alert, when the radar senses it cannot see completely through the storm, or the storm behind the storm.
A Dallas tv station had its own weather radar 15 miles from DFW. It was a ground-based version of the Arinc 700 airborne Wx radar, complete with doppler turbulence detection. At about the very moment DL 191 was on approach, the tv weather man showed and commented on the turbulent cell right over DFW.
You might ask why the FAA didn't have that same radar picture? Government incompetence reigns.
Why hadn't Delta retrofitted the valuable L-1011 fleet with the latest radar? The FAA didn't require it.
GB