I've relied on Bill's site for decades. I think I've even provided links to it here in years past. It's amazingly accurate, but like any forecast not always right. It's without a doubt correctly predicted pretty well all if not all of the biggest tropo ducts I've experienced. It's great to know in advance, for time management purposes, that I might be busy, say, the next Tuesday night. And the site doesn't usually let me down. In fact, it's arguably more accurate than the weather forecasts, though they all generally go hand in hand.