Prefix all of this with "apparently...", because I'm not exactly an AWIPS expert.
Meso filenames should begin with "MESO" rather than "MESO1" or "MESO2".
The source_scene attribute should be one of "Mesoscale-1" or "Mesoscale-2" rather than "Mesoscale".
I thought it best to get the ball rolling with this stuff rather than agonize over whether or not I could integrate things better. That said, I'm happy to any make changes!