Some trees will be restrained, yes, and every day (at CP at least) ride ops perform a track walk to check for branches/debris before ever testing the track. Then you send empty trains for a couple of circuits, then you send a test rider, so there's no risk of something happening overnight and remaining undetected until guests are riding.
If a storm of such intensity were to hit during the day, the same checks would be run before the coaster would reopen, of course. Granted, no, not all trees will show signs (there was a news item a few months back about a tree at Disney that just fell over without warning - you know that Disney would have caught it if there were signs!), but there are risks you take with anything you do. Yes, the coaster may be struck by lightning in a freak storm while you're on it if the storm is quick enough, etc.
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Po!nt of View: A different look at Roller Coasters.
http://www.crosswinds.net/~justmayntz/thrills/index.html