What is a 'bomb cyclone' and how does it form? After urgent warning is issued across three western states

A powerful storm is moving toward the West Coast that weather enthusiasts have coined a 'bomb cyclone.'

The term 'bomb cyclone' refers to any midlatitude cyclone that has undergone 'bombogenesis,' or a rapid increase in strength or magnitude over 24 hours, according to the National Oceanic and Atmospheric Administration (NOAA).

The storm occurs when a cold air mass collides with a warm air mass, which typically happens over ocean waters, the agency shared.

Storm intensity is measured by central pressure — the lower the pressure, the stronger - and is considered a 'bomb' when the pressure drops rapidly to at least 24 millibars in 24 hours.

Meteorologist Ryan Maue said that the central pressure of the upcoming bomb cyclone will fall almost 70 millibars in 24 hours, reaching pressure levels similar to that of a Category 4 hurricane.

The National Weather Service (NWS) alerted residents in northern California, Oregon and Washington to potential hurricane-force winds, catastrophic flooding and feet of high-elevation snowfall this week, with effects starting Tuesday.

This super-charged storm will bring wind gusts of up to 70 miles per hour, and pull a Category 5 atmospheric river onto land that will dump up to 20 inches of rain in certain areas.

A wind projection map showed gusts between 60 to 70 miles per hour from Eureka to Coos Bay and up the coast north of Aberdeen.

Places like Oregon's Klamath Falls, Bend and Penleton and Seattle in Washington can expected between 50- to 60-mile-per-hour winds. 

A precipitation map projected rainfall could reach up to five inches in north-central and northwestern California, western Oregon and western Washington, and northeastern California may see up to 20 inches.

Worldwide, about 40 to 50 'bomb cyclones' brew each year, but most are over open ocean and nobody but weather geeks notice, Maue said.

Alex Sosnowski, AccuWeather senior meteorologist, shared: ''The term bombogenesis comes from the merging of two words: bomb and cyclogenesis.

'All storms are cyclones, and genesis means creation or beginning. In this case, bomb refers to explosive development and altogether the term means explosive storm strengthening.'

A cyclone is a large air mass that rotates around a central point of low pressure. 

In the Northern Hemisphere, they spin counterclockwise and in the Southern Hemisphere, they spin clockwise and are therefore called 'anticyclones.'

A cyclone may undergo bombogenesis if it encounters a mass of warm, moist air, creating a significant temperature difference between the storm and its surroundings.

Over that temperature contrast, a powerful, intensifying jet-stream disturbance forces air to rise, and this kicks off the bombogenesis process as the cyclone's central pressure plummets, according to The Weather Channel.

That is because rising air produces a vacuum effect, resulting in lower atmospheric pressure. 

These intense storms typically form in winter, and are more common off the East Coast of the US that  experiences roughly one bomb cyclone per year. 

But they can form anywhere off the coast of the US. 

The term 'bomb cyclone' can also be used to describe tropical storms that rapidly strengthen. Hurricane Milton - which grew from a Category 1 to a Category 5 within a 24-hour period before slamming into Florida - was an example of bombogenesis. 

The impact of this bomb cyclone will be compounded by an atmospheric river - a long and narrow region of the atmosphere that carries warmth and moisture from the tropics toward the Earth's poles. 

The cyclone will direct a Category 5 atmospheric river toward the coast of the Northwest. A Category 5 is exceptionally hazardous, bringing intense storm impacts to land. 

Extreme storm systems like this bomb cyclone are likely being fueled by human-driven climate change in a number of ways, according to the Union of Concerned Scientists. 

For one, rising ocean temperatures create a greater contrast between over-land temperatures and the temperature of Arctic air moving south. Storms feed off of this ever-widening difference. 

Additionally, increasing evaporation from land driven by rising global temperatures pumps the atmosphere full of water vapor. When that vapor condenses into clouds, it releases latent heat, which storms use for fuel.

Increased water vapor also provides more moisture for storms, resulting in more frequent heavy precipitation events. 

Climate change is also increasing the number of days that the western US will experience atmospheric rivers, according to the US Department of Agriculture. 

And as warming air and ocean temperatures provide more fuel for atmospheric rivers to become larger and stronger, they will become more hazardous as well.