Take a hurricane moving up from the south. Mash in a colder storm moving in from the west. Add a ridge of high pressure extending through the atmosphere above the northeastern Atlantic Ocean and Greenland, blocking the typical flow of the jet stream. That’s the recipe for what will become “Post-Tropical Storm Sandy” or, as it has more colloquially been dubbed: “Frankenstorm.”
The result of all that atmospheric blocking is that instead of turning away from land and heading out into the northeastern Atlantic Ocean, this particular storm is going to be pushed ashore somewhere between Delaware and Long Island, New York. At the same time, it will be merging with the cold air coming in from the west—and that means Sandy will be the unusual hurricane that ends up producing snow in its western reaches.