An extratropical surface cyclone with a central pressure that falls on the average at least 1 mb hâˆ’1 for 24 hours. This predominantly maritime, cold season event is usually found approximately 750 km downstream from a mobile 500-mb trough, within or poleward of the maximum westerlies, and within or ahead of the planetary-scale troughs. Sanders, F., and J. R. Gyakum, 1980: Synopticâ€“dynamic climatology of the "bomb". Mon. Wea. Rev., 108, 1589â€“1606.