Explosive cyclogenesis (bomb cyclone or bombogenesis) occurs when an extratropical cyclone intensifies at an extraordinary rate: its central pressure falls at least 24 hPa in 24 hours (latitude-adjusted). This generates hurricane-force winds, extreme seas, and heavy precipitation.
Notable examples
Storm Klaus (2009) devastated south-west France and northern Spain with 200 km/h winds. The 1991 "Perfect Storm" and numerous Atlantic lows affecting Galicia and Spain's Cantabrian coast are examples. The phenomenon occurs over warm ocean currents (Gulf Stream, Kuroshio) where the thermal contrast between polar air and warm water is greatest.