"An intense low pressure system with a central pressure that falls 24 millibars in 24 hours" (UK Meteorological Office).
This is a predominantly maritime, cold-season (winter) event occurring at attitudes around 60 degrees north or south.
An explosive cyclogenesis occurs when dry air from the Stratosphere flows into an area of low-pressure. This causes air within the depression to rise very quickly and increase its rotation, which in turn deepens the pressure and creates a more vigorous storm commonly associated with strong destructive winds.
The four most active regions where extratropical explosive cyclogenesis occurs in the world are the Northwest Pacific, the North Atlantic, the Southwest Pacific, and the South Atlantic.
In the Northern Hemisphere the maximum frequency of explosively deepening cyclones are found within or to the north of the Atlantic Gulf Stream and Kuroshio Current in the western Pacific, and in the Southern Hemisphere, Australian east coast lows above the East Australian Current, which shows the importance of air-sea interaction in initiating and rapidly developing extratropical cyclones.
There are a number of factors which play a role in the triggering of explosive cyclogenesis:
- Baroclinic instability
- The proximity of strong Jet Streams
- Warm ocean currents
- Deep tropospheric frontogenetic processes which happen both upstream and downstream of the surface low