bomb cyclone

Also known as “explosive cyclogenesis,” this term refers to a rapidly deepening extratropical surface cyclone with a central pressure that falls on the average of at least 1 hPa h⁻¹ for 24 h, after applying an adjustment to a latitude of 60° using the following equation: r sin(60°)/sin(ϕ), where r is the observed pressure fall (hPa h⁻¹) and ϕ is the cyclone’s latitude. This adjustment accounts for variations in the geostrophic wind speed induced by equivalent pressure gradients at different latitudes. Consequently, it requires a larger pressure drop to qualify as a bomb cyclone at higher latitudes compared to lower latitudes. Colloquially, this process has been referred to as "bombogenesis."

This predominantly maritime, cold-season event is usually found approximately 750 km downstream from a mobile 500-hPa trough, within or poleward of the maximum westerlies, and within or ahead of the planetary-scale troughs.

Sanders, F., and J. R. Gyakum, 1980: Synoptic-dynamic climatology of the “bomb”. Mon. Wea. Rev., 108, 1589–1606, https://doi.org/10.1175/1520-0493(1980)108<1589:SDCOT>2.0.CO;2.

Term edited 22 December 2023.

A division of the year according to some regularly recurrent phenomena, usually astronomical or climatic.

1. Regular markings on an instrument used to allow the reading of the measured quantity or setting.

1. In general, pertaining to or affording an overall view.