What is a bomb cyclone? What to know about the weather term

CLEVELAND — On Nov. 19, 2024, a powerful storm struck the Pacific Northwest region of the United States. It became one of the most intense weather events in recent history. A powerful low-pressure system located off the Washington and Oregon coasts developed into a what we call a “bomb cyclone.”  

The storm brought hurricane-force winds, heavy rain and mountain snow to Washington, Oregon and Northern California within a short period of time. 

The storm brought massive destruction to the area, destroying thousands of trees and more than 450 miles of power lines.

About 600,000 homes lost power. Two people lost their lives as trees fell on homes and cars. Wind gusts reached hurricane force, topping out above 75 mph in some areas, and the mountain passes became nearly impassable under blizzard-like conditions.

Impacted communities took weeks to recover. 

Imagine sitting around a campfire enjoying the gentle flames. Now imagine throwing gasoline on that fire. What happens? 

An explosion of flames and heat within seconds that could send you running for cover. 

A bomb cyclone is a meteorological term that describes a low pressure system whose size, strength and intensity increase rapidly in just a short amount of time.

Technically, it describes a storm system whose central pressure drops at least 24 millibars within 24 hours. This rapid increase in strength is referred to as “bombogenesis.” The low pressure develops into a sudden, intense, often life-threatening storm. This rapid pressure drop causes winds to accelerate and rainfall or snowfall to intensify within a few hours. 

The November 2024 event produced a pressure drop exceeding twice the normal “bomb” threshold, which established it as one of the strongest bomb cyclones in recorded history.  

The storm develops when two distinct air masses meet in a forceful collision. 

The Pacific or Atlantic Ocean sends its warm moist air directly into the path of Arctic air which exists as a dense and cold air mass. The temperature difference between the warm and cold air masses creates atmospheric instability which leads to the formation of lift and fast-developing storms. 

Strong jet stream winds located above the surface create an atmospheric vacuum which causes air to rise and move away from the surface. The system experiences a rapid decrease in surface pressure because of this which enables it to develop into a powerful storm system. As the atmospheric pressure continues to decrease, the storm center develops stronger winds. 

These systems draw their moisture for clouds, rain and snow from nearby oceans with a tropical moisture connection with an almost unlimited supply of water vapor. The storm receives its strength from a “moisture pipeline” which produces heavy rain and snowfall that extends across several states.  

A bomb cyclone that reaches its full potential strength will produce destructive outcomes. 

Powerful winds can reach speeds of 70 to 80 mph. That’s strong enough to knock down trees, damage roofs and break power lines. 

The storms produce heavy rain that often exceeds several inches in short periods of time. That leads to life-threatening flash floods, mudslides and dangerous debris flows. Heavy snows, especially at higher elevations, cause dangerous driving conditions and road closures. 

The fast development of bomb cyclones creates a situation where people receive limited warning time to prepare for the most severe weather conditions. 

These systems extend their influence across multiple states which results in simultaneous wind damage and flooding and snow-related destruction, often for hundreds of miles.  

Bomb cyclones occur throughout the world but they show a particular preference for targeting a few areas of the United States.

The Pacific Northwest region often deals with bomb cyclones. 

The most active weather systems occur during the late fall and winter months because cold, Arctic air interacts with Pacific storms which carry warm, moist air. 

The East Coast – from North Carolina to Maine – also sees frequent bomb cyclones, often in the form of Nor’easters that rapidly intensify just off the coast over the Atlantic. 

Even parts of the Midwest and Great Lakes experience them from time to time, when fast-falling pressure systems bring howling winds and whiteout snow. 

Bomb cyclones occur, essentially, anywhere cold, dry air crashes into warm, humid air, especially near an ocean. 

The frequency of these storms appears to be increasing based on the data. Some scientists predict that ocean warming and increased atmospheric moisture will lead to stronger storms that might occur more often during the next several decades. The warmer ocean waters provide additional energy which leads to fast storm intensification through bombogenesis processes.  

While we can’t stop these storms, we can prepare for them. 

Check for severe weather alerts and forecasts which apply to your location. 

Secure outdoor furniture or trim tree limbs near your home. 

Store emergency supplies that include flashlights with batteries and food and water supplies. 

Stay informed about local news and weather reports when a significant weather system is on its way. Check your local forecast from this station’s trusted team of meteorologists.

The next bomb cyclone will occur and preparedness will determine whether you face minor problems or a catastrophic situation.