I didn't post here last night or today but I've been keeping up with Zeta. Here's a different point of view. Take a look and tell me what you think. It's done strengthening now and if you take a look at the WATL you'll be able to see the impact from the westerlies is beginning, and it'll be really evident by midnight or so. I think this shear has been enhancing the convection late this afternoon and early evening.

Take a look at the floater WV as well and you'll see that as the trough approached the air around Zeta became less dry. That 'electric shock' look to the convection (I don't mean the transverse banding on the outflow, but the core convection) the last couple frames is due to shear this time, not dry air intrusion.

It is the beginning of the end for the convection. However I don't have much information on how deep that trough is, or if it has weakened anywhere, and it is a possibility that with Zeta's continued slip to the south it may just survive (which is what the GFDL saw). But I think that's an outside chance. If it does, there's another area of low shear behind the trough.