All you need to know about Bomb Cyclones

A ‘bomb cyclone’ is also referred to as a ‘weather bomb’ or an ‘explosive storm’, but there’s no need to duck and cover. These names are actually rooted in the science of winter storms. Though it seems as if meteorologists are using hyperbole to draw in more viewers, for a storm to be classified as a ‘bomb’, it actually has to meet a stringent set of criteria. ‘Explosive bombogenesis’ occurs most often in the winter, and it’s almost always referring to a storm that tracks up the US East Coast. Typical surface air pressure tends toward 1010 millibars. Most of the big storm systems that sweep rain and snow across the US clock in around

995 or 990. But for a storm to rank a ‘bomb’, it must rapidly intensify and drop at least 24 millibars in 24 hours. The storm that rode up the East Coast was expected to have achieved of a 50-millibar drop in about 24 hours.

When a storm strengthens this quickly, it’s a signal of how much air is being drawn into the storm’s circulation. It then spirals inward toward the centre, rises, and then exits through the top. If more air is leaving the storm than is sucked inward, the pressure falls even more and the system will continue to grow. As the bomb storms strengthen — a process called ‘bombogenesis’, many of these storms are accompanied by very heavy rain or snow, coastal flooding, and hurricane-force wind gusts. Bombogenesis is a sight to behold from a meteorological perspective. It is most common in nor’easters, the gales spin up off the East Coast in the late fall and winter. They feed off the temperature contrast between the cold land and adjacent Atlantic waters still holding on to heat from the summertime. As much of the world experiences above-normal winter temperatures, the eastern United States remains in the frigid grip of an Arctic weather system known as the polar vortex.