More than simply a convergence of rain bands, the 53 inches of rain is anticipated due to four days of hurricane and tropical storm hovering just barely inland over the same area.
The hovering is predicted by GFS which is pretty crappy on hurricane tracks (see Sandy for example). Admittedly the Euro keeps the storm around for 2-3 days also. But I would not be cherry picking the GFS at this point.
Watch for all the global warming salesmen to come out in he wake of this Hurricane...along with the push for donations to bogus ‘help’ spams.