A bomb cyclone is a large, intense mid-latitude storm that has low pressure in its center, weather fronts, and a range of associated weather conditions, from blizzards to severe thunderstorms to heavy precipitation. It becomes a bomb when its central pressure decreases very rapidly – by at least 24 millibars in 24 hours. Two famous meteorologists, Fred Sander and Jean Gyakumgave his name to this pattern in a 1980 study.
When a cyclone “bombs” or undergoes bombogenesis, this tells us that it has access to the optimal ingredients for strengthening, such as large amounts of heat, humidity, and rising air. Most cyclones do not intensify quickly this way. Bomb cyclones put forecasters on high alert, as they can produce significant harmful effects.
The East Coast of the United States is one of regions where bombogenesis is most common. It’s because the storms in the middle latitudes – a temperate zone north of the tropics that includes the entire American continent – draw their energy from great temperature contrasts. Along the eastern seaboard of the United States in winter, there is a naturally strong thermal contrast between the cool earth and the heat Gulf Stream Current.
Above the warmer ocean, heat and humidity are abundant. But as cool continental air moves overhead and creates a large temperature difference, the lower atmosphere becomes unstable and buoyant. The air rises, cools and condenses, forming clouds and precipitation.
Intense cyclones also require favorable conditions above the surface. Particularly strong upper winds, also known as “jet streaks”, and high amplitude waves embedded in storm paths can help force the air to rise.
When a strong jet drag overlies a developing low-pressure system, it creates a feedback pattern that pushes hot air up at an increasing rate. This allows the pressure to drop quickly in the center of the system. As the pressure drops, the winds strengthen around the storm. Essentially, the atmosphere tries to equalize pressure differences between the center of the system and the area around it.
Meteorologists predict that the northeastern United States will be hit by a powerful winter storm on January 28 and 30, 2022. Forecast models predict a band of snow from the North Carolina coast north to Maine.
While the precise locations and amounts of snowfall are still uncertain, parts of the New England coast appear most at risk of receiving 8 to 12 inches or more of heavy snow accumulation. Coupled with forecast winds in excess of 50 miles per hour along the coast, the storm is likely to produce blizzard conditions, storm surge, coastal flooding, wind damage and beach erosion.
The life of this storm is expected to begin off the southeastern United States as a weak low pressure system. Just 24 hours later, global models predict that its central pressure will drop by 35 to 50 millibars.
If this storm develops as forecast, aided by winds blowing in excess of 150 miles per hour in the upper atmosphere, very warm sea surface temperatures just offshore (2 to 4 degrees Fahrenheit warmer than average) and a very unstable atmosphere, it will have the critical ingredients for a bomb cyclone.[Understand new developments in science, health and technology, each week. Subscribe to The Conversation’s science newsletter.]