When a storm makes landfall, meteorologists might refer to it as a “bomb cyclone.”
In recent years, the “bomb cyclone” has become a concerning meteorological phenomenon, especially during winter seasons. While 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 system formed by a rapid increase in atmospheric pressure over a short period. A low-pressure system is an area where atmospheric pressure at the center is lower than that of surrounding areas, causing swirling winds. Bomb cyclones can produce strong winds reaching speeds of up to 119 km/h, equivalent to tropical storm winds, but it is not a tropical storm.
Low-pressure systems frequently occur around the globe and are formed by moist air rising from the Earth’s surface. They often lead to unstable weather phenomena, such as overcast skies and heavy rainfall. However, when a low-pressure area moves beneath a strong jet stream of rapidly moving air from low to high altitudes in the atmosphere, it can create something much more intense.
Satellite image of explosive cyclogenesis (bomb cyclone) off the Eastern Coast of the United States in January 2018.
The jet stream will push air away from the low-pressure column, reducing its weight and causing sea-level pressure to drop even further. If the pressure drops by 24 millibars or more within 24 hours, this is described as explosive cyclogenesis. This is the official term for bomb cyclone.
As pressure drops, more air gets drawn in, causing the pressure column to spin faster, leading to peak wind speeds within a few hours. This can result in a powerful storm. These winds can be strong enough to uproot trees and damage the structures, putting lives at risk.
The term “bomb cyclone” is used because storms formed by this phenomenon often occur over the ocean, with a speed and ferocity rarely seen on land.
Scientists have even found that storms caused by “bomb cyclones” can induce tremors in the Earth. This occurs when waves collide, transmitting energy down to the ocean floor and beyond. In 2014, Japanese seismologists recorded tremors generated by a “bomb cyclone” forming off the coast of Greenland, located on the opposite side of the globe. This shows that “bomb cyclones” can generate strong vibrations that can travel significant distances.
Bomb cyclones form when atmospheric conditions at the surface and in the jet stream align to stimulate a rapid increase in low pressure. The jet stream is a band of strong winds high in the atmosphere, and a combination of complex atmospheric processes leads to these storms. Typically, bomb cyclones begin from a disturbance in the winds in the mid-levels of the atmosphere (about 5 to 8 km above the ground).
Four regions where bomb cyclones often form on Earth include the Northwest Pacific, North Atlantic, Southwest Pacific, and South Atlantic.
“Bomb cyclones” are not a rare phenomenon. Meteorologists estimate that such storms will erupt in the Northern Hemisphere about 10 times a year.
Low-pressure area refers to a region with lower atmospheric pressure than its surrounding areas. Low-pressure systems form beneath the wind divergence occurring in the upper levels of the atmosphere. The process of forming a low-pressure area is called cyclogenesis. In meteorology, a cyclone (also known as a vortex) is a large body of air rotating around a strong low-pressure area. Cyclones are characterized by winds spiraling inward and around a low-pressure zone. The troposphere is the lowest part of the atmosphere of some planets, including Earth. Most daily weather phenomena occur in the troposphere. This layer is characterized by convection currents of warm air rising from the surface and cooling down. The phenomenon of convection has given this layer its name. |
