The only problem with the park not having a central warning system is with those people who aren't out on the rides/in the stores at the time, and have no way of being warned. Please bear with me, it's storytime...
I, too, was working the day of the infamous waterspouts - a split shift (9:30am-1:30pm and 6pm-close) on the Iron Dragon. As those of you who were there know, the waterspouts hit during that "off" time. We'd had a bad thunderstorm the day before (no waterspouts), and we'd been told to evacuate the ride and seek shelter in restrooms, which we did. Well, when I went on my split on the waterspout day, I stopped by the Employee Cafeteria for lunch (I believe it was turkey that day), and took it up to my room (Gold Dorms, by Hotel Breakers). I noticed that the sky was getting dark and there was obviously a storm coming, but in all honesty it wasn't as dark or as windy as what had happened the day before, without waterspouts. I remember that the sky looked kind of yellowish/greenish, but that's not so bad, and it wasn't loud or anything. So I shrugged it off and continued reading my book. When I went back to work about 6pm, everyone was all excited asking me if I'd seen the waterspouts, and I had no idea that anything had happened at all! Go figure, the most exciting and photogenic weather phenomenon in my life, and I miss the whole thing with my nose in a book.
My husband (then fiance) saw it on CNN the next evening when he was shopping for a TV at Sears - even he got to see more of it than I have!
The moral of the story being, if the waterspout had come onto land and taken out the dorms (not that it would be hard!) there would have been no warning to those inside. I'm assuming that the same would be the case with a tornado, though I'm sure the debris would cause enough noise to warn people about the severity of the storm.
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PO!NT OF VIEW - A Different Look at Roller Coasters
http://www.crosswinds.net/~justmayntz/thrills/