Phenomenal bomb cyclone develops off the Pacific Northwest

An exceptionally powerful low-pressure system developing off the coast of the Pacific Northwest this afternoon is a sight to behold on satellite imagery.

The storm is undergoing bombogenesis—hence the “bomb cyclone” moniker. Bombogenesis occurs when a low-pressure system rapidly intensifies at a rate of about 24 millibars in 24 hours.

Our low-pressure system has more than doubled that rate of intensification. At the time of this post, its minimum central pressure had dropped from 981 mb to 955 mb in just six hours between 1200 UTC and 1800 UTC. It’s likely going to strengthen further heading into Tuesday evening.

Such a remarkable rate of intensification is a sheer display of the atmosphere’s power. 

A broad upper-level trough over the northern Pacific Ocean coincided with two jet streaks, or regions of stronger winds within the larger jet stream. Winds collide together and fan out as they blow around troughs and as they enter and exit these jet streaks. 

When winds fan out—or diverge—it leaves a void in the upper levels of the atmosphere that air from the surface has to rush upward to fill. This upward motion leaves less air, and lower air pressure, at the surface. This is how most of our everyday low-pressure systems develop and sustain themselves.

Multiple sources of divergence working together can force a massive amount of air to rise into the upper atmosphere, very quickly creating a powerful center of low pressure at the surface. That trough combined forces with the two jet streaks to rapidly intensify this storm as it swirls off the coast of the Pacific Northwest.

While the center of the storm will remain far offshore, folks on land are certainly feeling its effects.

Widespread high winds will likely lead to tree damage and power outages from Oregon to British Columbia. Flooding rains are also expected as the storm pushes a surge of tropical moisture ashore. Rainfall totals of 7-10+ inches are expected across sections of northern California through the weekend.

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