It’s not a word you hear every day, and you may not have encountered it before, but bombogenesis is very much in the headlines at the moment. It sounds dramatic—and it is. Bombogenesis is what happens when the atmospheric pressure associated with a midlatitude North Atlantic cyclone drops 24 millibars or more in the space of 24 hours. The lower the atmospheric pressure within a cyclone, the more intense the storm created.
This kind of dramatic drop and rapid intensification can occur when a cold air mass collides with a warm air mass, such as might be found over warm ocean waters. Bombogenesis is a popular term for what meteorologists call explosive cyclogenesis, and it became more widely used after the publication of a paper on the subject by MIT professor Frederick Sanders and his Ph.D. student (at the time) John R. Gyakum in 1980.
While it is not the case that just any old intense storm merits the use of this term, instances are more common than you might think. To take an extreme example, 14 of the 20 hurricane-force wind events that formed in the North Atlantic during the first two months of 2014 underwent bombogenesis. Storm Fionn, which battered Ireland and the UK this week, was one such storm, and just a couple of weeks ago another worked its way up the U.S. East Coast and had a major impact in the Northeast.
The result of this kind of rapid intensification is known as a bomb cyclone or weather bomb—names that sound much worse than such events generally are. The bomb cyclone just experienced in the northeastern U.S., however, was a particularly large and powerful winter storm. According to the National Weather Service, its pressure dropped 53 millibars in the space of 21 hours, making it one of the most explosive East Coast bomb cyclones ever recorded.
That storm deposited 12 to 18 inches of snow over much of New England, where it was also called a Nor’easter, and delivered wind gusts of up to 75 mph. If that weren’t enough, record low temperatures were experienced from coastal Virginia to New England, and some locations underwent blizzard conditions. And along the coast large waves and storm surge coinciding with high tides led to extensive flooding. According to the National Weather Service, Boston Harbor’s tide gauge reached 15.16 feet on Thursday afternoon, breaking the previous record set during the blizzard of 1978. New Jersey declared a state of emergency for Cape May, Atlantic, Ocean, and Monmouth counties, and New York City declared a winter weather emergency. Widespread travel restrictions were put in place, and millions of people stayed home. As well as wind damage there was, as expected, widespread coastal flooding, power loss, and business interruption.
Storm Fionn brought a similar cocktail of snowfall, brutal temperatures, damaging winds, power outages, and travel chaos to Ireland, southern Scotland, and parts of northern and eastern England this week. I don’t know about you, but I am so ready for Spring!