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11  January 2018, The Conversation, Explainer: ‘bomb cyclones’ – the intense winter storms that hit the US (and Australia too). The eastern United States experienced a very severe winter storm last week, which caused damaging winds, heavy snow and the highest tide on record for Boston. Meteorologists call this type of storm a “bomb cyclone”, or simply a “bomb”. But what is it? A “bomb” is an old meteorological term for a low-pressure system outside the tropics (that is, an extratropical cyclone) that intensifies very rapidly, based on how fast the atmospheric pressure drops at the centre of the storm. A common benchmark is a drop of 24 hectopascals (hPa) over 24 hours, although this varies slightly with latitude. The recent bomb in the US had a reported pressure drop of 59hPa over 24 hours, making it one of the strongest such storms ever recorded. Read More here