You've likely heard about a "bomb cyclone" impacting the Northeast this week. You've likely also never heard of a "bomb cyclone" before.
Truth be told, it's a portmanteau of two meteorological mouthfuls: bombogenesis and mid-latitude cyclone.
So let's breakdown what these two terms mean.
A "mid-latitude cyclone" is the technical term for a large area of low pressure located in the mid-latitudes (roughly between 30 degrees and 60 degrees north and south of the equator).
"Bombogenesis" describes the rapid development and strengthening of a mid-latitude cyclone, and it is defined as a drop of at least 24 millibars in central pressure within 24 hours (in the case of this early January 2018 storm, it is forecast to drop as much as 40 millibars as it moves up the Eastern Seaboard). Meteorologists note that a low is "bombing out" when it gets close to or reaches its peak strength, or minimum pressure.
Wind speeds increase as the pressure difference between the low and the surrounding areas intensifies; sustained wind gusts can reach as high as 55 mph during the peak of the storm. Precipitation also becomes more intense, resulting in heavy snowfall and potential blizzard conditions during winter storms. Heavy snow rates can also occur during bombogenesis, which is sometimes accompanied by lightning (a phenomenon known as thundersnow).
Bombogenesis is not new; it happens every fall through spring
If this is the first time you have heard of "bombogenesis", keep in mind that the term is not new in the meteorology world. As far back as 1980, the term has been used within a meteorological case study published in the Monthly Weather Review journal.
"Bomb cyclones" often occur every October through March as the strong temperature contrast between arctic air to the northwest and warmer, more humid air to the southeast interact within and strengthen the mid-latitude cyclone. The cyclone, or low pressure system, strengthens due to the baroclinic environment that sets up from the warm, less dense air to the south versus the very cold, dense air to the north. These low pressure systems are associated with cold fronts and warm fronts, and the wind speeds increase as the temperature change -- and effectively the pressure change -- occurs over large distances.
Previous storms to "bomb out" include the following months/years: