The National Weather Service tweeted a GIF of the storm descending into Northern California on Tuesday, calling it a “bombogenesis.” The GIF was shocking in itself, showing a cyclone-shaped cloud heading over the area via radar:
Satellite imagery shows rapid strengthening, or "#bombogenesis", of the mid-latitude cyclone off the coast of the Pacific Northwest. This system will bring a variety of inclement weather to #NorCal today thru Thanksgiving! #CAwx pic.twitter.com/2TPVlIfCPz— NWS Sacramento (@NWSSacramento) November 26, 2019
The GIF was a great indication of the storm on its way, but it also caused some confusion with this new word we’ve never seen. We hear about “atmospheric rivers” in the Pacific Ocean all the time, but rarely “bombogenesis.” So we had to find out – what the heck is a bombogenesis? Here is a definition from the National Oceanic and Atmospheric Administration:
Bombogenesis, a popular term used by meteorologists, occurs when a midlatitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours. A millibar measures atmospheric pressure. This can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters. The formation of this rapidly strengthening weather system is a process called bombogenesis, which creates what is known as a bomb cyclone.
In layman’s terms, a bombogenesis is a rapidly intensifying weather system of low pressure that occurs when cold air collides with warm air over the ocean, which strengthens the system. While the weather phenomenon isn’t rare, it’s also something that isn’t seen in this area regularly.
According to the NOAA, fourteen of 20 hurricane-force wind events underwent bombogenesis in the North Atlantic during the first two months of 2014. To be classified as a weather bomb, or having undergone bombogenesis or “bombing out,” the central pressure of a low-pressure system must drop at least 24 millibars within 24 hours.
The result of a bombogenesis? Typically a storm is intensified when it reaches “bombing out” and includes increased rain, snow, extreme wind and even lightning. The fact that the NWS used the term means that the storm has intensified significantly over the course of its development.
While the NWS has forecast up to 3 feet of snow across NorCal mountains, that could actually increase as the storm strengthens. In fact, the NOAA has indicated the storm could bring up to 4 feet of snow to the Sierra Nevada.
So it looks like the first storm of winter is going to more intense than initially expected. Here we go, Northern California – winter is here.