What is a ‘bomb cyclone’?

As the winds blow, the rotation of the Earth creates a cyclonic effect. The direction is counterclockwise in the Northern Hemisphere (when viewed from above).

John Moore, a meteorologist and spokesperson for the National Weather Service, said conditions for a bomb cyclone had been met over the Great Lakes, where frigid Arctic air from the meandering polar vortex met very warm air to the east.

Air pressure dropped to at least 962 millibars, while elsewhere it was as high as 1,047 millibars. “It’s a really sharp gradient,” he said.

As the area where the two air masses meet, called the Arctic front, moves northward and eastward, conditions for bombogenesis should continue moving as well, Moore said.

But as the Arctic air spreads over most of the country it will eventually warm, reducing the pressure difference. The storm will dissipate. And forecasts call for above-average temperatures across most of the country next week, he said.