What is Bomb Cyclone? 

• Storms can form when a mass of low-pressure air meets a high-pressure mass. The air flows from high pressure to low, creating winds. 
• What defines a bomb cyclone is how rapidly the pressure drops in the low-pressure mass — by at least 24 millibars in 24 hours. This quickly increases the pressure difference, or gradient, between the two air masses, making the winds stronger. This process of rapid intensification has a name: bombogenesis.
• 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).
• 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.
• But as the Arctic air spreads over most of the country it will eventually warm, reducing the pressure difference. The storm will dissipate. 

Why in News?

• Bomb cyclone enveloped much of the US recently.

reference:

https://indianexpress.com/article/explained/explained-climate/bomb-cyclone-united-states-canada-explained-8343764/