The atmospheric river season is here again. The first big storm of the Water Year of 2024-2025 is arriving, and it looks like a gigantic storm when seen from space.
The storm currently rolling off the northwest coast of the United States, which meteorologists have described as a “bomb cyclone,” is bringing atmospheric rivers. Strong winds and heavy precipitation are expected.
The image below provided by the National Oceanic and Atmospheric Administration shows a bomb cyclone and the atmospheric river below it dumping precipitation over Northern California and surrounding states.
A bomb cyclone approaches California on Wednesday.
(National Oceanic and Atmospheric Administration)
The past two winters have been unusually wet for California, and it’s unclear how this season will go, but this first storm is certainly off to a great start. This week’s weather event marks the first major atmospheric river in months. There have been dozens in the past two years.
The animation below gives a sense of the storm’s movement, rotating counter-clockwise and forming a classic cyclone as jets of moisture flow over the West Coast.
Seen from space, this storm is huge, spanning much of the North Pacific Ocean. Wave data showed swells of more than 20 feet in waters off Northern California on Tuesday as wind speeds exceeded 40 knots.
A very powerful bomb cyclone is helping propel this giant storm, but its impact is weakening as it intensifies farther from the coast.
Just because it’s officially a bomb cyclone doesn’t mean it’s the worst storm on record, Daniel Swain, a climate scientist at the University of California, Los Angeles, said in an online briefing. “There is bombing going on hundreds of miles west of the coastline.”
Although the name is dramatic, bomb cyclones are low pressure systems found north of the tropics and south of the Arctic that deepen or develop very quickly over a 24-hour period.
Officials said the system detonated at nearly four times the speed needed to be considered a bomb cyclone. Although the worst winds occurred offshore, the strong winds still bring strong winds to the Pacific Northwest and help push large atmospheric rivers toward the West Coast.
A bomb cyclone will hit the West Coast on November 20, 2024.
(Joint Atmospheric Research Institute/National Weather Service)
The animation below, from NOAA’s GOES-West satellite, shows the cyclone’s formation and movement up the coast.
More than 6 inches of precipitation is expected in many areas of Northern California through the rest of the week, according to the National Weather Service office in Sacramento. Light rain is expected in Southern California through the weekend.
In Northern California, significant precipitation is expected to arrive from the atmospheric river on November 20, 2024.
(Sacramento National Weather Service)
According to the Associated Press, the storm left about 38,000 Californians without power, and two people were killed by falling trees in Washington.
Experts are warning of the risk of flooding from heavy rain expected to fall across much of the Pacific Northwest in the coming days.
The Associated Press contributed to this report.
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