Bomb cyclones, intense winter storms with high winds, heavy blizzards and sub-zero temperatures, are basically winter hurricanes that are created through a process known as bombogenesis.
Bombogenesis is a weather term that combines "bomb" and "cyclogenesis," the creation of a cyclone. While bomb cyclones can happen in cold or warm months, they receive the most attention in winter.
Cold dry air and warm moist air collide to create a cyclone, a storm that rotates around a low-pressure center. Mid-latitude cyclones, named for their location, form in the band of space reaching roughly from south of Texas to the middle of Alaska.
A cyclone intensifies as warm air is pulled to its center and rises out of the top. As more air escapes, the air pressure drops and the storm gets stronger.
What defines a blizzard?: Heavy snow and high winds expected to sweep across country.
What is a bomb cyclone?: A winter hurricane, explained.
What happens during bombogenesis?
Bombogenesis occurs when the cyclone's central barometric pressure drops at least 24 millibars in 24 hours.
A millibar measures air pressure. A drop in millibars indicates lower air pressure, which indicates the storm is gaining strength, according to the National Oceanic and Atmospheric Administration.
How cyclones — and bomb cyclones — are created
First stage: A stationary front forms with dry cold air and moist warm air.
Second stage: The two fronts move against one another.
Third stage: The fronts begin to rotate around a low-pressure center.
Fourth stage: The cold air displaces the warm air, forcing it to rise. That fuels a change in temperature, which causes the air pressure to drop.
If the decrease in air pressure is severe enough — 24 millibars in 24 hours — bombogenesis takes place and a bomb cyclone results.
Are bomb cyclones the same as hurricanes?
Though bomb cyclones share characteristics with hurricanes, they are not hurricanes:
- Bomb cyclones have cold air and fronts. Cold air rapidly weakens hurricanes, while it is an essential ingredient for bomb cyclones.
- Bomb cyclones form during winter. Hurricanes form from late spring to early fall, while bomb cyclones form from late fall to early spring.
- Bomb cyclones form at higher latitudes. Hurricanes form in tropical waters, while bomb cyclones form over the northwestern Atlantic, northwestern Pacific and sometimes the Mediterranean Sea.
CONTRIBUTING George Petras/USA TODAY
SOURCE USA TODAY Network reporting and research