When and how does a bomb cyclone happen?

A bomb cyclone is officially a thing. But what exactly is a bomb cyclone? You might be wondering—what the heck is a bomb cyclone? Welcome to the strangest weather phenomenon of the season. But let’s start with where you live, not where it goes.

A bomb cyclone is, essentially, a low pressure system that generates the coldest air masses we can get in the continental United States. In other words, a bomb cyclone may look like snow in the northern parts of the country, while other parts of the U.S. will experience the coldest air we can get at this time of year. A bomb cyclone is born from a pressure drop, a very normal phenomenon in the sky that happens when warm air is pulled below freezing at the top and forms a dense cloud.

This phenomenon spreads in all directions and can affect areas as wide as the Atlantic Ocean. This is known as a bomb—and if you get one of these bombs near the equator, it’s technically a bomb.

What about the current weather pattern?

In terms of the long-term forecast, it seems like the weather pattern is in a “like-a-bomb-storm” mode. Therefore, we’re seeing very cold air over the northern United States, a storm track over the Great Lakes, and a low pressure system with a very strong pressure gradient over the northern Plains and upper Midwest.

How do you fall into an “and-b-and-g”?

The “t”s are upper-level features, low pressure, and the like. When you’re having a “bomb”—that is, having a low pressure system or low-pressure feature—then the warm, moist air mass at the surface is unable to rise and so rain or snow tends to fall instead of warm or moist air coming up. As that warms and condenses, the cold and dry air also falls, meaning precipitation. We call this a “bomb.”

Now, a “bomb” occurs in two parts. First, we have a weak surface low over the warmer ocean—like the Great Lakes—which creates both storm track and low pressure. The second part of the “bomb” is the pressure. Each part—the surface low and pressure gradient—constitutes the “plus” in our bomb-symbolizing classifications.

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