The first thing to assess is what the worst gust could be and whether the tree is strong and healthy (and some trees are more brittle than others...) Also, look out for dead hanging branches that could be dislodged by a heavy gust.

I guess the best way to be prepared for a swift exit is to have a rope suspended by it's mid point from a strong crotch high up in the tree. Make sure the two ends are tied together before you lower them down to the ground (and that the rope reaches the ground) so that you don't run out of rope on one side before you reach the bottom or you will accelerate at the terrible rate of 9.81m/sē!! This way you can rappel down both ropes together to ground level and pull the rope through afterwards to get it back (this is called a retrievable abseil in mountaineering). Being a rock climber too, I use a Sticht plate to abseil with. An Italian hitch can be used in the absence of an abseiling device - I'm sure there are books or rock climbing instructors who could show you this and other techniques.

One more thing I would say to any novice treeclimber - never use dead or sick-looking branches, no matter how thick - I trusted a dead branch about 6 inches thick when I was new to climbing trees - it broke almost immediately leaving me desperately trying to stay in the tree 35ft above a greenhouse It seems the weight of the branch alone was nearly enough to break it so all it needed was a delicate touch from me...

Sounds like you've got some serious surfing stories to tell - I'm not too keen on water myself so I'll stick to climbing (and snow)!