fb-pixelNew England weather: How atmospheric rivers impact the East Coast Skip to main content

Is atmospheric river flooding like what we saw in California possible on the East Coast?

Submerged trees stood in the flooded Los Angeles River during an atmospheric river storm in Los Angeles on Monday.Kyle Grillot/For The Washington Post

A double-whammy of atmospheric rivers slammed California this week, causing flash floods, landslides, and hurricane-force winds. As torrential rain fell across the state, massive waves crashed over breakwaters, drivers became trapped in floodwater, and neighborhoods were inundated.

While the phenomenon is commonly associated with the West Coast, atmospheric rivers also affect the East Coast — but they tend to develop differently and often go by a variety of other names, experts say.

An atmospheric river is a long plume of concentrated moisture that typically extends across the Pacific, said Zack Taylor, a senior meteorologist with NOAA.

They are most common during winter, can dump “copious amounts of rainfall,” and generate winds and waves, he said.


A mud-filled drive in Beverly Hills, Calif. on Feb. 5, 2024. JENNA SCHOENEFELD/NYT

Such plumes can also originate off the Gulf of Mexico or the Atlantic Ocean. However, “atmospheric river” is often not used to describe the phenomenon on the East Coast because “a variety of other factors” can bring rainfall and precipitation, Taylor said. Sometimes they’re described as a “frontal precipitation” or “moisture conveyor belts.”

Still, in the Northern Hemisphere, atmospheric rivers are pathways for tropical moisture to feed winter storms, including classic nor’easters, Alex Hall, an atmospheric physicist and climate scientist at UCLA, said in an e-mail.

In California, atmospheric rivers are colloquially known as a “Pineapple Express” when they’re aligned in the Hawaii-to-California direction, said Paul Ullrich, a professor of regional climate modeling at UC Davis.

But they can come in from a variety of angles and are almost always associated with “extratropical cyclones,” which are “very big, low-pressure systems that in the East are most commonly associated with winter storms,” he said.

“That’s where you get things like famous blizzards or snowmageddon or snowpocalypse,” said Ullrich, adding that by some measures, 50 percent of precipitation in the East is tied to atmospheric rivers.


The atmospheric river that inundated California this week left a trail of destruction. Officials said nine people died in the storms, the Los Angeles Times reported.

Kelly Mahoney, a research meteorologist at NOAA, said there are two main reasons why atmospheric rivers are not discussed as often on the East Coast.

The first is that visually — on satellite imagery — they are far more impressive in the West, with Mahoney likening them to “rivers in the sky.” In the East, they tend to look watered down “because we have so much moisture and so many different moisture sources.”

The other reason, she said, is the way the precipitation extremes and flooding happen on the West Coast “is almost literally like a fire hose of moisture in the sky that impinges on mountains.”

“In the East, you may have an atmospheric river, but the actual precipitation, it might be triggered by mountains, but more than likely it’s going to be the precipitation is essentially going to get wrung out of the sky, like squeezed out the atmospheric river,” she said.

“It definitely gets more distributed, and it’s a lot harder to anticipate where that rain is going to fall, so we typically don’t say the atmospheric [river] caused this thing,” she added.

As global warming increases, most of NOAA’s climate projections show there will be an uptick in the intensity of atmospheric rivers around the world, Mahoney said. Warmer air can hold more water.

“They will probably be more frequent,” she said, and there’s “potential for their impacts to be more severe.”


Shannon Larson can be reached at shannon.larson@globe.com. Follow her @shannonlarson98.