Spain had suffered through a dry, hot summer. Last week, as Barcelona's 1,750,000 people celebrated the Festival of Our Lady of Mercy, the agonizing drought ended. There was a promising thunderclap and as the winds rose, the city's lights failed; in darkness, Barcelonians climbed to the roofs of their houses to welcome the rain. But soon, as one woman put it, "the water turned into a monster."
Barcelona was in the path of a tornado. As the sky opened, every sun-baked gulch became a torrent. The dust-dry beds of the rivers on either side of Barcelona carried floods 75 ft. wide. Debris...