What is a bomb cyclone?

A bomb cyclone (technically: explosive cyclogenesis or bombogenesis) is an extratropical low-pressure storm that intensifies very rapidly. This means the air pressure at the centre of the low drops extremely quickly.

By convention, a low is considered a "bomb" when its central pressure drops by at least 24 hPa within 24 hours. This figure refers to about 60° latitude; for other latitudes there is an adjustment using a factor that accounts for the latitude dependence.

How does it form?

• Strong temperature differences (e.g. between cold air over land and warm ocean air)
• Amplification through the jet stream structure (strong upper-level winds)
• The release of latent heat through intense precipitation can further drive the intensification

Consequences and dangers

• Very strong gusts and hurricane-force winds
• Heavy rain or heavy snowfall, depending on temperature
• Storm surges along the coast due to low air pressure and strong winds
• Rapid spread and the potential for widespread storm damage