Zeta sorta looks like it's being sheltered from the worst of the shear by a weak upper-level low to its southwest, perhaps a feature that tailed off at the bottom of the trough that has been approaching it. It also appears that this trough is about to fracture, likely missing the storm until the next batch of westerlies gets to it in 24 hours or so.

Zeta's been helped by being as far south as it is. This upper low appears to be pivoting to the south and east around the southern side of the storm; if Zeta is deep enough vertically, it might be turned a bit more to the west or west-northwest for a brief period of time in response to this feature. It's probably deeper than it was a day or two ago, but still not terribly deep -- probably "moderately deep," a vague term I'm using to suggest a storm that probably extends to the 300-400mb level. If it moves further north, Zeta will meet those westerlies; even if it doesn't, the westerlies will likely get it at some point. There's a small chance that the upper low and the "sheltering" environment it seems to be providing sticks around and keeps Zeta going for the next few days, but any drastic change and the storm is done for.

It briefly displayed an eye-like feature on microwave imagery in the late afternoon hours, but that is gone now. Nevertheless, it has the appearance of a strong tropical storm on both microwave and conventional satellite imagery and was probably stronger in the late afternoon hours...but appears to have leveled off since and may have slightly weakened. I've got a hunch that the aforementioned trough that looks to be fracturing just to the west of the storm likely narrowed quite a bit in scope and actually helped contribute to the organization of the storm -- and not in weakening it as had been forecast. It has a little bit to do with the outflow and enhanced diffluence, topics Margie hinted at in her analysis. It's tough to predict such an evolution, however, and even tougher for these wildly atypical systems. The upper-low now is likely helping to maintain the cooler temperatures aloft; as a result of everything I've mentioned, I'd expect a steady-state storm for the next 24 hours or so (except for maybe any "corrections" upward in intensity) followed by slow weakening, perhaps a tad slower than the NHC forecast. Once the shear hits it, however, it should die fast.

We'll see how this all pans out, but it's hard to have a *lot* of confidence in anything but its ultimate demise right now.