What is a 'bomb cyclone' and how does it form?

'Bomb cyclone' occurs when a cold air mass collides with a warm air mass, which typically happens over ocean waters.

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

The 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.