NPR: As of Tuesday morning, for residents of the East Coast of the US, the worst of Hurricane Sandy has passed through, leaving flooded streets, downed trees, and millions of people without power. The damage is still being assessed as the storm makes its way toward Canada and the Great Lakes region. Not only is Sandy one of the largest hurricanes ever to strike the US, it is also extremely slow-moving and staying strong even as it moves across the eastern part of North America. In addition, it struck the coast during high tide and a full moon and coincided with a winter storm moving east from the central US. To discuss the many factors that make Sandy such a rare event, NPR’s Audie Cornish interviews Perry Samson, an atmospheric science professor at the University of Michigan.