Non-idiomatic "would be a rare X that Y": "...would be a rare hurricane that..."

I see what Bobbi means now, and agree that the phrasing is awkward because it is so close the the expression "it's a rare X that Y". The statement in context is saying that Irene (not a hypothetical hurricane as implied by the subjunctive) is one of those rare hurricanes. It would be better expressed as:

He said he was highly confident of the storm’s track, saying that it will be one of those rare hurricanes that travels right along the densely populated Interstate 95 corridor.

"meaning that" also contributed to the confusion, since the fact that it would track down the corridor is not something the writer could have inferred from "He said he was highly confident of the storm’s track", but rather confirming what had been said elsewhere in their conversation.

It's a rare wire reporter who can get it right every time, in my experience. I used to work for the Associated Press (on the tech side) and loved to bother the reporters with corrections.

There's a problem with the way you have provided the sentence in question: "He said he was highly confident of the storm's track, meaning it would be...."

The subjunctive "would" is here being used to describe what the speaker's intended meaning was, but we haven't got the actual context of the phrase to compare against what that meaning might actually be. Presuming this is what the speaker actually intended (and not, instead, that Mr. Read is disguising false logic with tricky prose), then there's nothing wrong about it. As for the idiom, you should take it as "It would be a rare [thing] that...."

As an example, consider if, for instance, these sentences were preceded by "[The scientist] stated that the Interstate 95 corridor was flanked on two sides by high mountains, which would cause the hurricane to lose much of its strength and be deflected out to sea. He said he was highly confident of the storm's track, meaning...."

In such a context, no -- the usage stands, and isn't all that idiomatic at all, so far as I can see. It's just standard syntax using a singular instance as a hyperbolic example, something rhetorically complex, but without any non-standard or dialectical oddity that I can see.

However, there is the possibility that it's misapplied, here, and without the preceding prose it's hard to say if it is or isn't. As given, and presuming that "meaning...." really is what the person quoted actually meant, in a context similar to that suggested above, then it's accurate.