Two weeks ago, Hurricane Helene slammed into the Deep South and parts of Appalachia, bringing devastating floods to a region often spared from strong hurricanes. A variety of factors combined to make Helene an especially dangerous storm. First, it formed over the Gulf of Mexico, where waters tend to be warmer than the Atlantic. Second, the globe is currently experiencing a transition to La Niña conditions where unusually cold ocean temperatures in the Pacific bring about all sorts of effects on the weather. Specifically, as it relates to hurricanes, La Niñas decrease what’s known as vertical...