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Bomb cyclone/ bombogenesis
Blinding snow whipped up by powerful winds pummeled the eastern United States on Saturday, as one of the strongest winter storms in years triggered transport chaos and power outages across a region of some 70 million people.
Major cities like New York and Boston bore the brunt of the blizzard, which the National Weather Service (NWS) confirmed intensified on Saturday into a “bomb cyclone” — characterized by the explosive power of rapid drops in atmospheric pressure.
A bomb cyclone is a large, intense midlatitude storm that has low pressure at its centre, weather fronts and an array of associated weather, from blizzards to severe thunderstorms to heavy precipitation.
It becomes a bomb when its central pressure decreases very quickly—by at least 24 millibars in 24 hours.
In simple terms, bombogenesis is a storm (low pressure area) that undergoes rapid strengthening. The vast majority of such storms occur over the ocean. The storm can be tropical or non-tropical in nature.
A cyclone (non-tropical storm or hurricane) is essentially a giant rising column of air that spins counterclockwise over the Northern Hemisphere.
When air rises, it produces a vacuum effect that results in lower atmospheric pressure. When a storm strengthens, the column of air rises at a faster and faster rate and the pressure within the storm lowers.
Storms, always have lower atmospheric pressure, but in this case the atmospheric pressure is lowering very quickly as the storm system intensifies.
Average storms in the winter have a low barometric pressure reading of 29.53 inches of mercury.
Some of the most intense storms may have a barometric pressure below 29.00 inches.
However, it is not the lowest pressure that defines bombogenesis but rather how quickly the pressure within the storm plummets.
When the barometric pressure falls at least 0.71 of an inch (24 millibars) in 24 hours, a storm has undergone bombogenesis.
The western North Atlantic is one favored area for storms to undergo bombogenesis. This is a region where cold air from North America collides with warm air over the Atlantic Ocean. Warm waters of the Gulf Stream may also provide a boost in a festering storm.
As a result, some, but not all nor'easters may undergo bombogenesis.
The intense winds often create massive seas and may cause significant beach erosion.
In terms of precipitation, very heavy rain and/or snow may fall in the path of the storm undergoing bombogenesis.
Precipitation rate is produced from the rising column of air. When air rises, it cools and moisture condenses to form clouds and rain or snow. The faster the air rises and cools, the heavier the precipitation.