What is a bomb cyclone?
Bomb cyclone is actually used by meteorologists to indicate a mid-latitude cyclone that intensifies rapidly. It is a massive winter storm hammering the coast, bringing strong winds, flooding, ice and snow. It is a combination of rapidly declining pressure and extreme cold. This particular storm is the most explosive ever, observed on the east coast. It is called bomb cyclone, a dramatic name for what happens when the storm explosively strengthens while the pressure plummets.
When discussing the storm, some weather forecasters have referred to a “bomb cyclone.” Calling it a “bomb” sounds dire, but those kinds of storms are not exceedingly rare — there was one in New England recently.
What makes a storm a “bomb” is how fast the atmospheric pressure falls; falling atmospheric pressure is a characteristic of all storms. By definition, the barometric pressure must drop by at least 24 millibars in 24 hours for a storm to be called a bomb cyclone; the formation of such a storm is called bombogenesis.
Here is how it works: Deep drops in barometric pressure occur when a region of warm air meets one of cold air. The air starts to move, and the rotation of the earth creates a cyclonic effect. The direction is counterclockwise in the Northern Hemisphere (when viewed from above), leading to winds that come out of the northeast — a Nor’easter.
That’s what happened at the end of October when warm air from the remnants of a tropical cyclone over the Atlantic collided with a cold front coming from the Midwest. Among other impacts then, more than 80,000 electric customers in Maine lost power as high winds toppled trees.