More than half a million Americans and 100,000 British Columbia residents were without power Wednesday morning as they battled a weather phenomenon known as a “bomb cyclone.”

The powerful storm swept across the northwestern US, lashing the region with high winds and rain, causing widespread power outages and toppling trees, killing at least one person.

In B.C., highways were closed, trees were downed and many were without power Wednesday.

But what is a bomb cyclone?

Global News chief meteorologist Anthony Farnell said the phenomenon is not new.

“This is something that has become very popular on social media recently, but it’s actually a meteorological term that has been around for decades,” Farnell said.

Meteorologists Fred Sanders and John Gyakum gave this pattern its name in a 1980 study.

A bomb cyclone is a large, intense mid-latitude storm with low pressure at the center, weather fronts, and a range of associated weather events, from blizzards to severe thunderstorms to heavy precipitation.

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According to the U.S. National Oceanic and Atmospheric Administration (NOAA), bombogenesis, a term used by meteorologists, occurs when a midlatitude cyclone (the latitudes between the tropics and the polar regions) rapidly intensifies or strengthens over a period of 24 o’clock. .

“If you have a rapidly intensifying cyclone that deepens 24 millibars in 24 hours or less, so about a millibar per hour, that would be a bomb cyclone. This more than doubled that. In fact, it has almost tripled: 66 millibars in 24 hours,” said Farnell.

Bombogenesis can occur when a cold air mass collides with a warm air mass, such as air over warm ocean water, according to NOAA. Colloquially it is called a bomb cyclone.

Most cyclones do not intensify quickly in this manner.

Bomb cyclones put forecasters on high alert because they can have significant damaging effects.

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Thousands without power after storm

According to Reuters, the East Coast of the US is one of the regions where bombogenesis is most common. That’s because storms in the midlatitudes — a temperate zone north of the tropics that encompasses the entire continental U.S. — derive their energy from large temperature contrasts.

Intense cyclones also require favorable conditions above the surface. Particularly strong winds at higher levels, known as “jet streaks,” and high-amplitude waves embedded in storm tracks can help push the air upward.

When a strong jet streak moves over a developing low-pressure system, it creates a feedback pattern that causes warm air to rise faster and faster. This can cause the pressure in the center of the system to drop quickly. As pressure drops, the winds around the storm become stronger. Essentially, the atmosphere tries to compensate for the pressure differences between the center of the system and the area around it.

Experts warn that extreme weather events are likely to become more common as the climate continues to change and warm.

Ryan Ness, director of adaptation at the Canadian Climate Institute, said reducing greenhouse gas emissions and adapting to the future must go hand in hand.

“We must prepare for a future where these types of events occur more often and are more intense. And that means building our infrastructure. It means making sure we protect areas from flooding, like along the coasts of British Columbia,” Ness said.

“The return on investments in adaptation is actually very high. It may seem like a costly investment in advance to build a bridge so that it is one and a half times as high to allow water to pass underneath, for example. But the costs if you don’t have the costs to replace that bridge, if it washes away, are obviously much higher.”

–With files from Reuters

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