[Tcoat]

OK so I just went and used the age old stud finding method and tapped on my door until the noise changed. They is indeed something very solid and straight right there (go try it). I am going to go with Spud's first thought that the door panel or that support is somehow vibrating and pushing it out. If it was a one off and stay the way it originally started then I would guess it had been pushed in but since it keeps getting worse that means it is dynamic and not static.

Could also be the ice thesis but I can't tell if it would hold enough water there to create enough force to push it out like that. I still think ice would have created a much larger bulge.