Bomb cyclone

A bomb cyclone, or bombogenesis in meteorological terms, is a rapidly intensifying low-pressure weather system. 

The "bomb" part of the name comes from the explosive rate at which the storm's central atmospheric pressure drops—specifically, it must fall by at least 24 millibars within 24 hours. This rapid drop in pressure causes the storm to strengthen dramatically, often leading to severe weather.

Formation and characteristics

Bomb cyclones typically form when a cold air mass collides with a warm air mass, often over warm ocean waters like those found in the Gulf Stream off the U.S. East Coast. This creates a sharp temperature gradient, which provides the energy for the storm to intensify quickly. 

A key characteristic of a bomb cyclone is its rate of intensification, not necessarily its overall size or strength. While all storms are cyclones (rotating low-pressure systems), most don't intensify this fast. 

The swift drop in pressure creates a powerful vacuum effect, causing surrounding air to rush toward the center of the storm at high speeds. This process fuels the storm's destructive potential.

The impact of bomb cyclones

The intense strengthening of a bomb cyclone can lead to a variety of severe weather conditions, including:

• Hurricane-force winds: The pressure difference generates extremely high winds, which can cause widespread power outages, down trees, and damage infrastructure.
• Heavy precipitation: The rapid rising of air causes moisture to condense, leading to intense rainfall or heavy snowfall, which can result in flooding and blizzard conditions.
• Coastal impacts: When they form over oceans, bomb cyclones can generate massive waves and storm surges, causing significant coastal erosion and flooding.

How common are they?

While the term "bomb cyclone" might sound like a once-in-a-generation event, the phenomenon itself, known as explosive cyclogenesis, is not as rare as it seems. 

On average, there are about 70 such storms globally each year. About two-thirds of these occur in the Northern Hemisphere, with a significant number forming off the east coasts of the United States and Japan, particularly during the winter months. 

The term gains public attention when one of these storms impacts a heavily populated area with a dramatic drop in pressure, leading to significant weather impacts.

Who coined the term?

The term "bomb cyclone" was coined by two prominent meteorologists: Frederick Sanders of MIT and John R. Gyakum of McGill University. 

In their 1980 article published in the Monthly Weather Review, they defined "bomb" as an extratropical cyclone that undergoes a rapid intensification, or "bombogenesis." 

The informal use of "bomb" to describe powerful storms goes back even further, to the 1940s and 1950s, among meteorologists at the Bergen School of Meteorology.

Similarities to a hurricane

While bomb cyclones and hurricanes are different types of storms, they share some key characteristics that make them both powerful and destructive:

• Low-pressure systems: Both are rotating, low-pressure systems. The lower the central pressure, the more intense the storm.
• Strong winds: Both are capable of producing hurricane-force winds (74 mph or greater), which can cause widespread damage, power outages, and coastal erosion.
• Heavy precipitation: Both can generate immense amounts of rain or snow, leading to flooding and dangerous travel conditions.
• Rapid intensification: A key similarity lies in their ability to intensify rapidly. The rapid intensification of a hurricane is a phenomenon called "rapid deepening," which is the tropical equivalent of bombogenesis

Understanding the key difference from a hurricane

Bomb cyclones are a powerful weather phenomenon that, while not rare, can have devastating impacts when they hit populated areas. 

Unlike hurricanes, they are "cold-core" storms fueled by the clash of air masses in mid-latitudes, typically during colder months. Understanding the unique characteristics of a bomb cyclone—specifically, its explosive rate of intensification—is crucial for recognizing the serious risks they pose to infrastructure and human safety through their high winds, heavy precipitation, and coastal impacts.