weather January 6, 2023 11:03 am What Is a Bomb Cyclone? The term “bomb cyclone” describes a storm that’s rapidly intensifying. The weather event happens when the atmospheric pressure of the storm drops 24-millibar (the unit that measures atmospheric pressure) in 24 hours. US & World Videos 4:11 Jeff's forecast: Heavy rain ahead 2:48 Forecast: Dry today, rain tomorrow 3:05 Vianey's forecast: Dry today, rain tomorrow 3:27 Jeff's forecast: Atmospheric river rain timeline 3:46 Jeff's forecast: Atmospheric river to bring heavy Bay Area rain