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http://en.wikipedia.org/wiki/Bomb_(meteorology)

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Bomb is a term for a low pressure area characterized by a rapid pressure fall. When this occurs with an offshore low, severe damage to coastal areas can result -- can produce central sea-level pressures, winds and coastal flooding comparable to those of weak or even moderate tropical hurricanes. ^[1]

Weather bomb an accepted meteorological label. ^{[2] [3]}

Sanders and Gyakum took the standard of 24 mb drop in 24 hours from Tor Bergeron’s earlier work on rapid intensification. In extending the Norwegian’s [sic] work, they ,

At a latitude of around 45 degrees North yesterday’s pressure drop needed to be only 19 mb to qualify. (The latitude of Bergeron’s Bergen, Norway is above 60 degrees North.)-

explosive deepening as surface pressure falls at a latitudinally adjusted rate of at least 1hPa per hour for 24 hours. The latitudinal adjustment for an equivalent pressure fall at 60˚N is achieved by multiplying the actual pressure fall by a factor of sin φ/sin60˚, where is the latitude of the cyclone centre. so if a cyclone develops around 45˚N with a rate of deepening 22hPa during 24 hours, is larger than the threshold for explosive deepening.

when very cold air from the continent moves over the ocean, accompanied by strong atmospheric dynamics . This creates an unstable baroclinic extreme.

Although their cyclogenesis is completely different from that of tropical cyclones, they will produce winds of the same order as the first categories of the Saffir-Simpson scale. They will also give strong precipitation . Some of these storms have caused extensive damage along the coasts of all continents."

"A rapid drop in atmospheric pressure in extratropical cyclones is due to large forces exerted by the jet stream. When pressures come down from more than one millibar per hour, we call such a bomb cyclone , . These bombs are rapidly dropping the pressure to less than 980 hPa when conditions are favorable, such as close to natural temperature gradients as the Gulf Stream in addition to a frontal zone already in the atmosphere. The greater the divergence in the upper layers, the greater the storm strengthens. These extratropical cyclones have a power comparable to a hurricane and make the most of the North Atlantic and North Pacific from mid-November and late February ." (section translated from wiki.fr) " Rapidly intensifying - Indicates an expected rapid intensification of a cyclone with surface pressure expected to fall by at least 24 millibar (mb) within 24 hours."

http://weather.ou.edu/~mbergman/bombcyclogenesis/index2.html

EOTS ^[4]

Superbomb and Ultrabomb

Ren,Perrie,Long,Gyakum,Atmosphere-Ocean coupled dynamics of cyclones in the midlatitudes,Mon Wea. Rev,v132,Oct2004,p2432-. they report and analyse a storm in the NW atlantic in Jan 2000 that dropped 42hPa in 24hrs.They termed this a 'Superbomb',and compare and contrast it with the extratropical transition of Hurricane Earl (1998) The most dramatic deepening rate I've found is the intensely studied ERICA IOP4 storm 4-5January 1989 which dropped 60hPa in 24hrs.This has been termed an 'Ultra bomb',see Weatherwise April 1999p76. Super Bomb Cyclogenesis: defined to be a pressure drop of 24 mb in 12 hours, normalized at 60 deg N Latitude (Bergen, Norway); translates to about 19 mb in 12 hours at 40 N; on Sep. 10, 1978, low pressure off the NJ coast (over the Gulf Stream) dropped 60 mb in 24 hours, battering the ocean liner "QE-II" and sank the fishing vessel "Captain Cosmo" ^[5]

^[6]

A robust signature in the Lorenz energy cycle is observed; anomalous energy conversions commence 48 h before explosive cyclone development and remain strong (i.e., significantly above background noise) for 120 h. Remarkably, the calculated signature of energy conversion is virtually identical for all four geographical regions. While the conversions imply a classic baroclinic growth cycle, they are not seen in regular cyclones that undergo a deepening of less than half that exhibited by explosive cyclones. This finding opens a new avenue of exploration of explosive storm behavior based on the large-scale environment. ^[7] Lorenz energy cycle- http://science.nbcnews.com/_news/2013/02/25/17088963-look-out-meteorological-bomb-is-on-the-way?lite

Such characteristics are associated with difficulty of prediction and also with serious threats to human life and property. ^[8]

ultrabomb 10 mb per hour for 6 hours. MWL 1990 https://babel.hathitrust.org/cgi/pt?id=uiug.30112104094252;view=1up;seq=17

wider use

In North America the term is also used in a wider sense than the strict meteorological definition.

http://www.tiempo.com/ram/4070/el-concepto-de-ciclognesis-explosiva/

https://www.wunderground.com/cat6/january-thaw-sight-after-two-week-wintry-onslaught-and-bomb-cyclone

N Am bomb used in wider sense - http://www.canadiangeographic.ca/tv/videos/video_description.asp?showNumber=23053

http://wattsupwiththat.com/2013/02/11/a-new-buzzword-for-pushing-climate-fear-explosive-cyclones/

References