'Once-in-a-generation' winter storm freezes US: What is a bomb cyclone

Bomb Cyclone In US: The National Weather Service (NWS) said temperatures of -50F (-45C) and -70F were possible by the end of this week in some parts of US.

A powerful Arctic winter storm has placed more than 135 million people under weather alerts ahead of the busiest travel days of the year in the US. The plunging temperatures could wreak havoc across the US and Canada. The storm could lead to frostbite on bare skin in only five to 10 minutes, experts have said. Weather alerts stretch from coast to coast and reach as far south as the US-Mexico border and Florida.

Bomb Cyclone In US: Pedestrians make their way along Halsted Street during a cold weather front.(Reuters)

Major airports have cancelled thousands of flights as the storm intensifies as the storm could bring the iciest Christmas in decades, say forecasters. The National Weather Service (NWS) said temperatures of -50F (-45C) and -70F were possible by the end of this week in some parts of US.

Meteorologists have also said that the winter storm could become a "bomb cyclone" by Friday.

What is a bomb cyclone?

A bomb cyclone is a storm that intensifies very rapidly. These form when air near Earth’s surface rises quickly in the atmosphere, triggering a sudden drop in barometric pressure of at least 24 millibars within 24 hours. As the air rises, wind spirals in at the base of the storm. As long as the air continues to rise at the top of the storm faster than it can be replaced, barometric pressure will continue to drop.

Why is it called a bomb cyclone?

Meteorologists have compared the sudden drop in pressure to a bomb going off, using words such as “explosive cyclogenesis” and “bombogenesis” to describe the storm’s formation process. Therefore, the term bomb cyclone is used as it refers to the speed at which a storm forms and not necessarily its absolute strength.

How does a bomb cyclone differ from a hurricane?

Hurricanes tend to form in tropical areas powered by warm seas. For this reason, they’re most common in summer or early fall, when seawater is warmest.