Hurricane Sandy’s New Jersey landfall on 29 October 2012 caused massive treefall that produced widespread, long-duration power outages throughout the landfall region. Using radar data and two independent types of models, we discovered that very large roll vortices, the largest ever reported, occurred in the lowest few kilometers of the troposphere over land during the landfall period. Roll vortices are helical flows that rotate on horizontal axes and lie next to each other near the ground, with adjacent rolls rotating in opposite directions. On the side of their downward motion, they transport higher-speed air to the ground, increasing the likelihood of damaging winds in localized ground-level streaks. Understanding their downward and upward air transport is also important for improving the accuracy of hurricane intensity forecasts.