There's some explanation here: http://epawablogs.com/the-great-halloween-hybrid-named-sandy-2/ http://epawablogs.com/the-great-halloween-hybrid-named-sandy...

There's some explanation here: http://epawablogs.com/the-great-halloween-hybrid-named-sandy-2/ http://epawablogs.com/the-great-halloween-hybrid-named-sandy... The gist is that there's a high-pressure system sitting over Greenland, and a large storm over the mid-Atlantic, which are predicted to push it westwards, where it'll interact with and be pulled into an existing continental weather system.