The season of atmospheric rivers is again upon us. The 2024-2025 water year’s first major storm is arriving, and from space it looks like a behemoth.
The storm currently off the northwest coast of the U.S. — described by meteorologists as a “bomb cyclone” — brings with it an atmospheric river. High winds and intense precipitation are expected.
The image below from the National Oceanic and Atmospheric Administration shows the bomb cyclone and the atmospheric river below it dumping precipitation on Northern California and surrounding states.
A bomb cyclone approaches California on Wednesday.
(National Oceanic and Atmospheric Administration)
The past two winters have been uncommonly wet in California, and while it’s unclear how this season will turn out, this first storm is certainly kicking it off to an impressive start. This week’s weather event marks the first major atmospheric river in months; the last two water years saw dozens of them.
The animation below gives a sense of the storm’s motion, spinning counterclockwise and forming a classic cyclone as a jet of moisture flows from it over the West Coast.
Seen from space, the storm is enormous, spanning a large portion of the Northern Pacific ocean. Wave data showed swells of more than 20 feet in the waters off of Northern California on Tuesday as winds exceeded 40 knots.
The exceptionally strong bomb cyclone is helping drive this monster storm, but because it intensified so far from the coast, its effects are diminished.
Just because it’s officially a bomb cyclone, that doesn’t mean it’s the worst storm on record, Daniel Swain, a UCLA climate scientist, said in an online briefing. “It’s bombing out hundreds of miles west of the shoreline.”
Though dramatic in nomenclature, a bomb cyclone is a low pressure system found north of the tropics and south of the Arctic that deepens, or intensifies, very rapidly over a 24-hour period.
This system did so at a rate almost four times what is necessary to be deemed a bomb cyclone, officials said. The worst of its winds occurred offshore, but the intense system still brought major winds to the Pacific Northwest and is helping push the large atmospheric river towards the West Coast.
A bomb cyclone hits the West Coast on Nov. 20, 2024
(Cooperative Institute for Research in the Atmosphere / National Weather Service)
The animation below, from NOAA’s GOES-West satellite, shows the formation of the cyclone and its movement up the coast.
Many areas in Northern California can expect more than six inches of precipitation through the rest of the week, according to the National Weather Service office in Sacramento. In Southern California, light rain is expected over the weekend.
Northern California is expected to see heavy precipitation from the atmospheric river arriving on Nov. 20, 2024
(National Weather Service, Sacramento)
Some 38,000 Californians were without power as a result of the storm, and two people in Washington were killed by falling trees, the Associated Press reported.
Experts warn of flood risk from the heavy rain expected to fall on much of the Pacific Northwest in the next several days.
The Associated Press contributed to this report.
