Weatherz School: What is ‘bombogenesis?’
Powerful weather systems sometimes make national headlines as ‘bomb cyclones.’ This ominous term was introduced by meteorologists to describe a storm system that strengthens very quickly.
Bomb cyclones happen when areas of very cold air collide with very warm air. Oceans often supply the warmth. The large temperature difference leads to rapid intensification, or explosive intensification, which is why it’s referred to as ‘bombogenesis.’
The criteria for ‘bombogenesis’ is the central pressure drops 24 millibars in 24 hours. This can happen any time, but it’s most likely from October to March. This is when Arctic air sags south and the ocean maintains high temperatures. Bombogenesis can result in very heavy precipitation and produce winds in excess of 70 mph.
We’ve seen these kinds of storms in the Northland. One example is the infamous Halloween Blizzard of 1991. Heavy snow fell with as much as 2” per hour while winds regularly gusted between 30 and 40 mph. Duluth’s final snow total for the storm surpassed three feet.
On November 1st, the low deepened and strengthened rapidly as it moved from western Illinois to the Upper Peninsula of Michigan. Minimum pressure fell about 24 millibars in 24 hours, classifying as bombogenesis.
Not every bombogenesis event is as historic as the Halloween Blizzard, but the heavy snow and strong winds from that day are what to prepare for when a ‘bomb cyclone’ is in the forecast.