A bomb cyclone has wreaked havoc on much of the United States over the past couple of days bringing brutal cold, busted water pipes, flooding and heavy snow.

Many of you are probably wondering what the term bomb cyclone means and where it originated. Let’s dive into the wonders of strong low pressure systems!

What is a bomb cyclone?

This term refers to a low pressure system that strengthens rapidly over a short period of time. The overall strength of low pressure systems is often tied to how low the pressure at the storm center is. The lower the pressure is at the storm’s center, the more intense the storm is.

The pressure of a storm system in meteorology is measured in units called millibars. A bomb cyclone is generally defined as a low pressure center that drops 24 millibars in pressure during a 24-hour period which results in rapid strengthening of the storm system.

I say generally because the definition is technically a function of the latitude at which the storm is at (more on that later).

Satellite image of the “bomb cyclone” that occurred on Saturday.

Basically, this is a way for meteorologists to differentiate between run-of-the-mill low pressure system and strong low pressure systems.

Why is it called a bomb cyclone?

The term originated in a scientific research article from the October edition of the Monthly Weather Review in 1980.

Frederick Sanders and John R. Gyakum, scientists from MIT, state that the term “bomb cyclone” was first used by a Swedish scientist by the name of Tor Bergeron while witnessing a rapidly deepening cyclone.

The term bomb was used because of the immense amount of energy these storms produce after rapidly strengthening.

How do you determine if a cyclone is a “bomb cyclone”?

The general definition is a pressure drop of 24 millibars in 24 hours, but the definition changes given the latitude of a storm.

The pressure drop required for bomb status is calculated by taking the sine (dust off the trigonometry knowledge) of the latitude where the storm is located and dividing it by the sine of 60 degrees (this is the latitude where Tor Bergeron originally created the definition). Then, you multiply that number by 24 and you get the amount of pressure drop required to be a bomb cyclone.

For example, the storm that has affected our area the past couple of days had a pressure of 1001 millibars at 7 p.m. Thursday night at a latitude of around 42 degrees north.

Therefore, the pressure drop required to be a bomb cyclone would be 18.5 millibars in 24 hours. The low pressure system deepened 31 millibars to a pressure of 970 millibars in 24 hours. This was an extremely strong storm system!

That easily achieved “bomb cyclone” status! Now you can do your own calculations any time there is a big storm nearby.