What is a weather bomb and how powerful is it?

When a hurricane makes landfall, meteorologists may call it a 'weather bomb' (bomb cyclone).

In recent years, the 'bomb cyclone' has become a worrying meteorological phenomenon, especially during the winter. Although it shares some characteristics with tropical storms, a bomb cyclone is not a tropical storm.

A bomb cyclone, also known as explosive cyclogenesis, is a powerful low-pressure vortex that forms from a rapid increase in atmospheric pressure over a short period of time. A low-pressure vortex is a low-pressure system where the atmospheric pressure at the center is lower than that of the surrounding areas, causing vortex-like winds. A bomb cyclone can produce winds as strong as 73 mph (119 km/h), equivalent to tropical storm force, but it is not a tropical storm.

Low pressure areas occur regularly across the planet and are formed by moist air rising from the Earth's surface. They often cause unstable weather, such as heavy clouds and heavy rain. However, when a low pressure area passes beneath a strong vortex of air moving rapidly from low to high in the atmosphere, it can create something much more violent.

Satellite image of the formation of an explosive cyclone (weather bomb) on the East Coast of the United States in January 2018.

The vortex pushes air out of the low-pressure column, reducing its weight, causing the pressure at sea level to drop even further. If the pressure drops by 24 millibars or more in a 24-hour period, this is described as an explosive cyclone formation. This is the official name for a 'weather bomb'.

As the pressure drops and more air is drawn in, the pressure column begins to rotate faster and faster, resulting in strong winds that peak over a period of several hours. This causes a severe thunderstorm. These winds can be strong enough to blow down trees and damage structures, putting people at risk.

The name 'weather bomb' is used because the storms formed by this phenomenon often appear at sea , with a speed and devastating power rarely witnessed on land.

Scientists have even found that storms caused by 'weather bombs' can cause Earth to shake. This happens when waves collide, transmitting energy to the ocean floor and beyond. In 2014, Japanese seismologists even recorded tremors from a 'weather bomb' that formed off the coast of Greenland, on the other side of the globe. This suggests that 'weather bombs' can create vibrations strong enough to travel far.

Bomb storms form when atmospheric conditions at the ground and in the jet stream are suitable to stimulate the growth of a strong low-level vortex. The jet stream is a band of strong winds in the upper atmosphere and a combination of complex atmospheric processes create these storms. Typically, bomb storms begin with a disturbance in the winds in the mid-atmosphere (about 5 - 8 km above the ground).

The four regions where explosive cyclones (weather bombs) commonly form on Earth include the Northwest Pacific, North Atlantic, Southwest Pacific, and South Atlantic.

'Weather bombs' are not an uncommon phenomenon. Meteorologists estimate that these types of storms erupt in the Northern Hemisphere about 10 times a year.

A low pressure area (depression) is an area of ​​lower atmospheric pressure than surrounding areas. Low pressure systems form below the wind dispersion zones that occur in the upper troposphere. The process of forming a low pressure area is called cyclogenesis.

In meteorology, a cyclone (also called a cyclone) is a large mass of air rotating around a strong low-pressure area. A cyclone is characterized by winds swirling inward and around a low-pressure area.

The troposphere is the lowest part of the atmosphere of some planets, including Earth. Most of the day-to-day weather occurs in the troposphere. This layer is characterized by convection currents of warm air rising from the surface and cooling down. This phenomenon of convection gives this layer its name.