The spiders gave away the scale of what was coming. Had they remained in their webs, Velma Del Rosario would have stayed home, too. It was October 24, 2018, late in the season for a storm. Velma had initially believed it would be small, a “banana typhoon”—the local term for the spells of rain and wind that wash over the Northern Mariana Islands every year, snapping the banana trees. Super typhoons were rarer, arriving only once a decade.

Earlier that afternoon, Velma had gone about her usual preparations. At four o’clock, she left the Veterans Affairs office where she…