Maps showing differences in vertical wind shear (top) and temperature (bottom) across the Atlantic hurricane basin during active versus quiet hurricane eras

Differences in vertical wind shear (top) and ocean surface temperature (bottom) between the active hurricane era of 1993-2015 and the preceding quiet period from 1970-1992. In active periods, the main development region for hurricanes has weaker shear and warmer temperatures, which favor major hurricane development. The pattern is reversed in U.S. coastal areas, however. Map by NOAA, based on data from Kossin 2017.