What is a bomb cyclone? What to know as Northern California braces for atmospheric river
Northern California could see heavy rain, mountain snow and powerful winds as an atmospheric river-fueled storm system sweeps the region.
Up to 10 inches of rain could fall in some areas while wind gusts could reach 70 mph, according to the California Governor’s Office of Emergency Services.
About 3 to 4 inches of rainfall was expected in the Sacramento area alone, the National Weather Service said.
“This one ... will kind of stall out along Northern California and bring many days of moderate to steady rainfall,” Courtney Carpenter, weather service meteorologist, said in a Monday news release. “We’re not expecting widespread flooding at this time but again, a lot of rain is going to cause some issues across the northern portion of the state.”
Meteorologists warn that the storm system could develop what weather experts call a “bombogenesis,” commonly referred to as a “bomb cyclone.”
Here’s what you need to know:
What is an atmospheric river?
“Atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics,” the National Oceanic and Atmospheric Administration said.
“The average atmospheric river carries an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River,” NOAA said on its website.
When an atmospheric river “makes landfall,” it often releases this water vapor in the form of rain or snow, according to NOAA.
“Those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods,” the federal agency said.
What is a bomb cyclone?
“A bomb cyclone is essentially a storm, a low-pressure system that strengthens by a matter of 24 millibars in 24 hours,” National Weather Service meteorologist Scott Rowe told The Sacramento Bee in January 2023. “The lower the pressure, the stronger the storm.”
A millibar is a unit of atmospheric pressure.
Cold air mass collides with a warm air mass and creates a bomb cyclone, according to the weather service.
Rowe told The Bee on Tuesday that a bomb cyclone strengthens wind speed along the coast.
It can also intensify winds further onshore — even as far inland as Sacramento, he said.
This story was originally published November 19, 2024 at 2:55 PM.
