A ‘bomb cyclone’ and ‘nor’easter’ could be in the forecast for the East Coast this weekend. What are they, exactly?

Meteorologists are warning of the approach of another major winter storm that could become a nor’easter intensifying into a bomb cyclone across parts of the East Coast this weekend. The storm is forecast to bring heavy snow, gusty winds and coastal flooding. It’s expected to rapidly intensify along the Atlantic Coast, and it could result in several inches of snow over much of North Carolina and parts of southern Virginia as early as Friday night through the weekend.

“Blizzard conditions are likely in some areas due to strong winds and low visibility as the evolving nor’easter intensifies into a bomb cyclone,” AccuWeather reported.

You may have heard the terms “bomb cyclone” and “nor’easter” before. If you’re not sure what they mean, Yahoo has you covered.

What is a bomb cyclone, exactly?

It’s a powerful low-pressure system that intensifies rapidly. It’s a process that meteorologists call bombogenesis.

The “bomb” part happens when pressure inside a storm cell falls so quickly that it gives the storm explosive strength. The scientific term “bombogenesis” refers to a storm that drops at least 24 millibars of pressure within 24 hours. A millibar is a unit of measurement meteorologists use to describe pressure, or the force exerted by the air’s weight. A low-pressure system is an area where the pressure of the atmosphere at sea level is lower than in the surrounding area.

When winds converge in the region, they rotate in the same direction as the Earth and can form a cyclone in the center of the area. This circulation carries air higher into the atmosphere, where moisture condenses into precipitation.

The lower the pressure drops within a cyclone, the more intense the storm.

What is a nor’easter?

A nor’easter is a large, intense area of low pressure that can produce heavy rain, heavy snow, severe coastal flooding or even blizzard conditions in the East. Such storms typically form along the Atlantic Coast and move northward or northeastward, according to the National Weather Service.

What’s the difference between a bomb cyclone and a nor’easter?

A bomb cyclone is a term meteorologists use to describe how fast a storm strengthens, while a nor’easter describes the location of where and how it forms.

It’s possible for a nor’easter to be called a bomb cyclone if it intensifies enough, which can lead to heavier precipitation and stronger winds than in a more slowly developing storm.

What are some of the worst bomb cyclones the U.S. has experienced?

One of the most extreme examples of a bomb cyclone occurred in March 1993, when the “Storm of the Century” brought blizzard conditions, hurricane-force wind gusts and coastal flooding from the Gulf Coast to New England. The storm claimed the lives of over 300 people from Florida to Maine, causing more than 10 million power outages and more than $5.5 billion in damage.

In January 2018, a storm rapidly intensified off the Southeast coast, targeting parts of the Mid-Atlantic and New England. It packed heavy snow, damaging winds, and record coastal flooding. The storm killed at least 20 people and caused $1.1 billion in damage.