Welcome to winter. If you’re on the east coast of the United States, your ‘bomb cyclone,’ aka winter storm Grayson, has arrived.  A state of emergency has been declared in New York City and surrounding areas as a massive winter storm is bringing heavy snow and high winds to the region. Boston residents are experiencing widespread flooding.

But what is a ‘bomb cyclone?’  It sounds pretty ominous but basically, it’s when the barometric pressure in the center of a big winter storm drops rapidly, intensifying the storm.  And Grayson is a big one.  Satellite pictures look remarkably like a hurricane with a central ‘eye’ and counter-clockwise rotation.  The Washington Post has a good explainer here.