Vince's formation isn't all that much unlike the S. Atlantic storm last season. It'll meet up with baroclinic sources before making landfall, unlike the S. Atlantic storm, but it's an interesting system nonetheless. The persistent eye-like feature probably forced the NHC's hand.

It's not really the SSTs that are the sole contributor to tropical cyclone development in the midlatitudes -- instead, it is the temperature differential between the SSTs and the upper-levels. If a system has colder-than-normal temperatures at the top of the troposphere, it can over come less-than-critical SSTs to form into a tropical cyclone. Obviously, this requires low shear and all of the other factors that lead to tropical cyclone formation!

Nevertheless, it's rare to have any tropical system east of 20W. The map we made for the season only went out to to 20W, as I didn't think we'd need anything in the teens. Shows how much I know!