To answer Margie's question: the distinction, at times, can be quite subjective. That's likely what happened here. We're trying to make it more objective, but when model resolution and data availability isn't enough to complete the task, a small subjective factor is introduced. That's probably what we're seeing here.

To answer Frog's question: they discontinued advisories as it was no longer a tropical system. Non-tropical systems can produce high winds -- as people along the Washington and Oregon coastlines have seen the past few days -- even to hurricane force, yet have no characteristics of tropical systems. Delta had transitioned into such a storm, thus the handoff by the NHC.