‘Bombogenesis’ Hits California

One of California’s strongest storms in years – dubbed as “bombogenesis” or “weather bomb” – has hit the state, killing at least four people and bringing torrential rain and floods.

Power cuts hit 150,000 households and sinkholes swallowed cars. Hundreds of homes were evacuated amid fear of mud slides near Los Angeles.

The storm looks to be the strongest storm to hit southwest California this season. It is likely the strongest within the last six years and possibly even as far back as December 2004 or January 1995.

Gusts of 87mph (140km/h) were reported on the Big Sur scenic coastal highway.

Explosive cyclogenesis (also referred to as a weather bomb, meteorological bomb, explosive development, or bombogenesis) refers in a strict sense to a rapidly deepening extratropical cyclonic low-pressure area.

To enter this category, the central pressure of a depression at 60° latitude is required to decrease by 24 mb (hPa) or more in 24 hours.

This is a predominantly maritime, cold-season (winter) event, but also occurs in continental settings. This process is the extratropical equivalent of the tropical rapid deepening.

Baroclinic instability has been cited as one of the principal mechanisms for the development of most explosively deepening cyclones.

However, the relative roles of baroclinic and diabatic processes in explosive deepening of extratropical cyclones have been subject to debate (citing case studies) for a long time.