The wind surprised us. That's a bit embarassing; to live in Oklahoma and be surprised by the weather. Sure, we'd watched the warnings on the local television station, but the bad part of the storm appeared to be passing north of us and we were distracted by an urgent family situation. Suddenly it pounced, a strong west wind with possibly some rotation. I knew it was serious when I heard the downstairs commode gurgling. The sound was not unlike that of the last bit of soda being sucked through a straw, except in this case the straw was the vent pipe on the toilet, three inches in diameter and twenty-five feet long.