Weatherz School: Bombogenesis revisited

As all eyes are on a winter storm impacting pre-holiday travel in the Midwest, we’re taking a look back at a topic we’ve covered in Weatherz School and applying it to what’s headed our way.

First, let’s establish what the term ‘bombogenesis’ are referring to. This ominous term was introduced by meteorologists to describe a storm system that strengthens very quickly. A storm that undergoes this kind of rapid intensification can be referred to as a ‘bomb cyclone.’

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.

This winter storm is expected to meet criteria as a ‘bomb cyclone.’ If we look at the mean sea level pressure starting at 6 pm Thursday, the center of low pressure will be near Indiana with minimum pressure of around 1003 mb.

The following 24 hour period is when the system is expected to undergo bombogenesis. The system will rapidly intensify as it tracks to the border of southern Ontario and Quebec by 6 pm Friday. By that time, surface pressure is expected to be as low as 970 mb, falling more than 30 mb in 24 hours.

The path of the storm will direct most of the snow east of the Northland across the Great Lakes into southern Canada. However, we will be grazed by snow on the western edge of the system. We’ll also experience strong winds.

Remember, winds are caused by differences in pressure. As the low intensifies, the winds around it will strengthen, and that’s why blowing snow will be a key concern Thursday evening through Saturday morning.

The combination of strong northwest winds and very cold air over Lake Superior will make the South Shore the target for lake effect snow. These communities will receive the greatest snow totals from this system in the Northland.