A "weather bomb" is set to bring heavy wind and rain to the UK this weekend as Storm Brian makes its way across the country.
The weather system, such as the one moving across the Atlantic Ocean, is caused when the central pressure in an area of low pressure falls rapidly.
The pressure has to fall by 24 millibars in 24 hours to qualify.
In a weather bomb, also known as explosive cyclogenesis, a jet stream of strong winds high up in the atmosphere interacts with the low pressure system.
The jet stream removes air from the low pressure system, reducing its weight and causing the pressure to fall.
As the pressure drops, air is sucked in from the surrounding area, which means the low pressure system spins faster and faster.
The Met Office describes the phenomenon as working in the same way that an ice skater spins faster by drawing their arms in.
On its website the weather service says: "The resulting winds peak over a period of a few hours and can be strong enough to bring down trees and cause structural damage."