How an unnamed storm brought a 1,000-year rainfall in the Carolinas

A tropical rainstorm — which fell just short of being named “Helene” — brought devastating flooding to portions of North Carolina on Monday, deluging streets and leaving neighborhoods under feet of water. More than 20 inches of rain fell by early afternoon, qualifying the event as a 1,000-year rain event — or one so rare it has a 0.1 percent chance of happening in any given year. According to the National Weather Service, 17.7 inches in 12 hours is the threshold for what constitutes such a statistically rare rain event...