One evening this spring, I was out to dinner when a curious thing caught my attention. The Weather Channel was on TV in the background, and every few minutes the camera cut to a radar shot of Fort Lauderdale, where a lone storm cell sat stationary over the city. There it continued to sit, refusing to move inland to dissipate or blow out to sea. I had never seen anything like it. Neither had Fort Lauderdale, where on that day, April 12, nearly 26 inches of rain fell in approximately 12 hours. Fort Lauderdale is not a one-off. In too...