[Crannogman]

Regardless of your sub class, the possibility of you keeping pace with a CVBG while ducking its aircraft is pretty remote. My guess is that the same group ran around your northern flank, allowing them to get ahead of you in the strait. I can't prove this, of course, but it seems more likely than the game spawning a new group in front of you because you're out of torpedoes.

In some cases, some shipping routes are inexplicably routed through land. My understanding is that the game only spawns actual ships when within a certain range of you; the rest of the time they are an abstract group tracked but not bound by the laws of physics. I checked stock and RSRDC but found no such groups in your reported location in time-space