Thank you for (re-re-re-?)posting this link. Fujiwhara Effect, eh? I have been out of the loop about the physics of this storm, and now I actually believe I understand it. I applaud the UKMET model teams, and then others, for their brilliant programming, analysis and computation. The BAMM clearly needs reworking, since it was completely clueless as late as Saturday. I have not been exposed to this behavior in weather systems before this hour, though I definitely have seen it in other systems.
Thank you, MetMom, Nelson, and others here for the education.
I ought to also opine that, given the failure of UKMET compared with GFS with Debby earlier, it is clear that both models have some way to go.