I would not cover it. If it was an older unit that didn't have the new(er) Aloca coating on it as your unit does, I'd say sure, but in wind, the cover will rub against the finish and from what I've read here, it will rub enough to eventually damage it.
A good washing and Walbernizing should help protect the finish as much as can be expected with something exposed to the elements. Ideally, you'd like to have it inside, but when it's not possible.......
One other suggestion with outdoor parking is that you cover the tires. UV, the elements take their toll on the rubber. I read that here too, and it isn't an Airstream exclusive either. Trailer tires I've read take more abuse than car tires, covering them when not in use seems to be highly recommended.
Computers manufactured by companies such as IBM, Compaq and millions of others are by far the most popular with about 70 million machines in use worldwide. Macintosh fans note that cockroaches are far more numerous than humans and that numbers alone do not denote a higher life form. -NY Times 11/91