Bomb cyclones are hurricanes that form in winter.
The "bomb cyclone" phenomenon is responsible for the extremely cold weather that is currently affecting the majority of America. As the bomb cyclone is expected to bring blizzard conditions and high winds to a large portion of the United States during the upcoming Christmas week, let's take a closer look at this extratropical surface cyclone's history, definition, and effects.
What is a bomb cyclone?
A bomb cyclone, or bombogenesis, is a quickly intensifying storm that occurs when air pressure drops 20 millibars or more within 24 hours. This usually happens when a warm air mass collides with a cold one, according to the National Oceanic and Atmospheric Administration. This time air from the Arctic ploughed into tropical air from the Gulf of Mexico, forming a depression bringing rain and snow.
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According to the American Meteorological Society glossary, "an extratropical surface cyclone with a central pressure that falls on average at least 1 mb h-1 for 24 hours. This predominantly maritime, cold season event is usually found approximately 750 km downstream from a mobile 500-mb trough, within or poleward of the maximum westerlies, and within or ahead of the planetary-scale troughs."
The history of this term
According to CNN, The term can be traced back to a meteorological research paper published in a 1980 edition of Monthly Weather Review. Its authors, MIT meteorologists Fred Sanders and John Gyakum, built upon work by Swedish meteorology researcher Tor Bergeron, who had initially defined "rapidly deepening" storms as those that met the 24 millibars-in-24 hours criterion.
What stands out about this storm?
What makes this storm extraordinary is just how fast the pressure dropped - 40 millibars in 24 hours, according to meteorologist Yann Amice of analysts Weather'n'co.
"This has led to the development of extreme storm conditions near the core of the low pressure system, with particularly harsh conditions," said Cyrille Duchesne, a meteorologist from the French Weather Channel.
The unprecedented nature of this storm comes from the intensity and extremity of its low temperatures, Duchesne said.
"That's what makes it exceptional," he said.
The impact level of the storm
The US National Weather Service said this "once in a generation type event" has the power to turn deadly and is already breaking cold-weather records with temperatures falling to minus 53 degrees Celsius (minus 63 Fahrenheit) in western Canada, minus 38 in Minnesota, and minus 13 in Dallas. It's even snowing in subtropical northern Florida.
Combined with blizzards and snow, the wind chill in regions like the Great Plains can make it feel like minus 55 degrees. The US National Weather Service warned that such cold can lead to frostbite on exposed skin within a matter of minutes, hypothermia, and even death if exposed to these conditions for too long.