Re a dedicated “weathership” best I can find at the moment is this, part of a much longer piece about John Young in airspace mag:
The day of the Challenger launch, Young was flying the weather plane, circling the pad, keeping an eye out for storms, wind, and temperature changes. From his aerial perspective, he saw it all happen. “We were holding at 20,000 feet and watching them lift off, and I got a picture of the whole thing blow—coming apart,” he says.
AFAIK the weathership pilot’s main job was checking conditions at low and medium altitude, primarily to make sure conditions were Ok for a Return To Launch Site (RTLS) abort, so Young might not have ventured up to the sort of altitude the shear was encountered.
https://www.airspacemag.com/space/spaceman-7766826/