from a friend....
there was some kind of mini-tornado in cayo in 1991 or 92. we were living on maya ranch then, mile 4.5 pine ridge rd. i was alone in the main house - and it took every piece of roofing (nailed not screwed) off of the guest house close to me, whirled trees around until they were felled on every side of me. the main house had a wrap around veranda, covered by main roof. all of the support 4 x 4's holding up the roof along the edge of the veranda were pulled out of their holes and set next to the holes on the veranda. with a little more wind we surmised that the entire roof structure, not just roofing, would have gone flying. that roof was screwed on. john used jacks to hike up the entire roof up again to put them back into the holes. close by in upper barton creek, it not only took down giant trees but it put a buggy up into a friend's roof - leaving it hanging there by the hames stuck in the thatch. it also had done some damage in spanish lookout before jumping south to the maya ranch/barton creek area.
was it a tornado or not, i don't know but it sure caused a lot of havoc. when i saw all the torn metal roofing (all blown into the same area west of the main house) i was thankful my guardian angel had been on duty that afternoon. it happened in the towards the end of the dry season and was not accompanied by rain.
you are right though - all roofs should be screwed on for sure. and large trees should not be planted too close to structures, even though the shade can be glorious.