The Brief

California is in the midst of a strong atmospheric river that's caused flooding, evacuations, road closures, and mention of it is all over the news and social media. And this comes on the heel of twoprevious winters where the Golden State saw damaging storms of the same kind. If you have the feeling that in the past few years, you've started hearing the term a lot more, you are not alone. You're not even wrong.

In recent years, "atmospheric river" has become used much more frequently in scientific papers and in media coverage. According to experts who study climate and weather, a couple reasons may explain why. Technical weather terms in general are now more used in the news. Atmospheric rivers are a thriving area of research, more of which may be filtering into media coverage. And these storms are also expected to intensify and become more damaging as the climate warms – which means there's more attention on them.

What is an atmospheric river anyway?

Before we get into why we're hearing about them more, let's go over the basics of what an atmospheric river is.

These storms have always existed. They occur around the world, often on the west coasts of the mid-latitudes, where an ocean meets a landmass. They're long filaments of concentrated water vapor in the lower atmosphere occurring along with strong winds – and they're the primary way water is moved horizontally. In California, a normal winter might see five of these kinds of storms and as many as 20 could occur during wet winters. A typical one can be 300 miles wide, a mile deep and 1,000 miles long. When plotted on a map or looked down upon from a satellite in space they looked just like rivers.

For a long time, they were colloquially and scientifically referred to as things like the Pineapple Express or Rum Runner Express. Those turned out to be just a subset of atmospheric rivers however, ones that originated near Hawaii or in the Caribbean heading toward Europe. Not all ARs are particularly warm or begin in those locations.

"So the 'atmospheric river' term is the broader envelope," says Daniel Swain, climate scientist at the University of California.

The term was coined in a 1994 paper by two researchers at the Massachusetts Institute of Technology.

"And it turns out that they are very comparable to terrestrial rivers in terms of how much water is moving in them," Swain said. "In fact, sometimes they're significantly greater even than some of the flow of the largest terrestrial rivers on earth," including the Mississippi or Amazon River.

How we talk about the weather has changed

Swain believes that one reason people are suddenly hearing about atmospheric rivers more is because those who communicate about weather to the public have made a shift to using terms that the scientific community uses.

"I think a lot of it probably has to do with the media landscape and the popularization of certain technical weather terms," he said, pointing to "bomb cyclone" and "bombogenesis" as other examples. These are formal, quantitatively defined meteorological terms, "and everyone assumes that's just some invention of the social media hype era."

In fact, he says, these seem to date back to the 1940s during World War II when meteorologists were advising Allied forces in the North Atlantic Theater.

Atmospheric river, he says, is similar.

"Instead of just making something up out of the ether," Swain says, "there's been an interest in what are actually meaningful, technically correct scientific terms to describe various weather phenomena, which I'm not so sure is a bad thing."

Scientists have done a lot to understand atmospheric rivers better

In recent years, ARs have been a blooming area of research, some of which is filteringinto mediacoverage.

Marty Ralph, director of the Center for Western Weather and Water Extremes at Scripps Institution of Oceanography, has been a pioneer in the field and is frequently cited in the press.

Researchers like Ralph have helped discover how important atmospheric rivers are, both for California but also for storms around the country and world. Back in 2004, the topic had fallen out of favor, says Ralph. But with new data collected by aircraft and satellites he showed researchers how to see the storms in a new way, allowing scientists to observe them from the inside and out.

"I sort of resurrected the topic after an early pullback," Ralph said.

This now-vibrant area of research has made some recent discoveries, says Ralph, including how to better predict their effects, how they impact both snowfall and snowmelt in the polar regions and links between AR intensity and climate change.

"Because a warmer atmosphere holds more water vapor and water vapor is the fuel in atmospheric rivers, ARs can carry more water vapor," Ralph says. "And there are studies now that show we can expect to see somewhat more extreme ARs and more common, in some cases, just because of that."

The weather news in California has flipped from being about drought to being about storms

What may increase the impression that atmospheric rivers are a new thing is that for a good part of the past decade, California was in serious drought and wasn't getting them. Then in early 2023, multiple AR storms followed one after another, resulting in flooding around California and 22 deaths.

"In both cases, it's a story about atmospheric rivers, in one case a deficit of atmospheric rivers, not enough of them, and the other case overabundance – too many atmospheric rivers all at once," said Swain. "California water lives and dies by this."

Atmospheric rivers are at fault in more than 80 percent of flooding across the West. On average these storms cause $1 billion in damage each year.

A look at Google Trends, reveals an early blip of interest in atmospheric rivers in early 2011, hardly anything during the drought years of 2012-2016, then more blips in 2017, 2019 and 2021 coinciding with West Coast storms and flooding. And finally large spikes in interest in 2023 and 2024. So far this fall has only brought one AR to California, but it is a record-breaking one.

A major development for the future of atmospheric river research, says Ralph, is the possibility of improving our forecasting up to two weeks before a storm.

Legislation introduced on Wednesday by Senators Alex Padilla (D-Calif.) and Lisa Murkowski (R-Alaska) seeks to secure funding to increase airborne reconnaissance – using planes to fly through the storms – to learn more about atmospheric rivers.

"The more we sample these storms, the more accurate the forecasts become," said Ralph.

Felt around the country

Lest you think these storms are purely a West Coast phenomenon, researchers are increasingly appreciating ARs role in fueling and directing nor'easters, strong storms that impact the East Coast.

"It's quite possible that AR recon in the Gulf of Mexico and off the East Coast will actually be able to improve the forecast scale of the track and intensity of nor'easters," Ralph said, "which people in the East know full well, is a very important detail in order to determine if the big cities are impacted."

NPR audiences first heard about atmospheric rivers in 2013, when Jon Hamilton offered "Tips for Surviving a Mega Disaster."

Since last summer, the Trump administration has been arresting undocumented immigrants as they try to claim their children from federal custody, stranding the kids in government shelters and foster care. The practice violates the government’s own regulations, according to an informal network of immigration attorneys across the country, who suspected for months that the arrests were the result of a formal policy.

Now, a document unearthed in a federal district court case in Texas appears to confirm that suspicion. “Operation Guardian Trace,” as it’s called in the document, requires Immigration and Customs Enforcement to conduct in-person interviews with the relatives of undocumented children in federal custody, and detain and deport those adults who are “illegally present in the United States.”

Immigration attorneys say the policy represents a dramatic reversal in how the government handles the release of unaccompanied minors and treats their undocumented relatives, who were previously allowed to get their children back regardless of their immigration status.

“This confirms what we’ve known for months,” said Mishan Wroe, directing attorney for immigration at the National Center for Youth Law in Oakland. “The government is explicitly and deliberately using children as bait to achieve their political goals.”

A copy of a U.S. Homeland Security department Form I-213, found in a federal immigration case file that’s under seal. In the document, a federal agent references Operation Guardian Trace, which requires ICE to conduct in-person interviews with the relatives of undocumented children in federal custody, and detain and deport those adults who are in the country illegally.

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Image courtesy of the Galveston-Houston Immigrant Representation Project.

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The children, who entered the U.S. alone and without authorization and have usually come to join family, are in the custody of the Office of Refugee Resettlement, part of the U.S. Department of Health and Human Services. They’ve often fled violence or persecution in their home countries, Wroe said, and most apply for asylum or other legal status. They’re detained until the government can vet their relatives, or sponsors, to make sure the adults can “provide for the physical and mental well-being of children.”

When a sponsor is detained, their application to claim the child is invalidated. If no other potential sponsors come forward, the child remains in ORR custody until they can be placed in foster care or they turn 18. Largely due to stricter sponsor vetting requirements put in place by the current Trump administration, the average number of days that children remained in ORR custody increased to 117 in 2025 from 30 the year before, according to the agency’s website. The data does not make clear how sponsor arrests have impacted that increase.

Nationwide, more than 100 sponsors have been arrested while trying to get their kids out of detention since July, 2025, according to internal government data obtained by The California Newsroom. That means roughly one in four sponsors who came in for interviews or I.D. checks were arrested. It’s unclear how many have been deported, or were later released and allowed to sponsor their kids.

Marion “Mickey” Donovan-Kaloust, legal services director at Immigration Defenders Law Center in Los Angeles, said her organization alone represents 12 children detained in Southern California whose parents were arrested shortly after coming forward to begin the process of getting their kids back. She said dozens more of her clients have relatives who are afraid to try to claim them because they fear deportation.

“It's part and parcel of the chaos and cruelty that's marking this administration's approach to immigration policy,” said Donovan-Kaloust. “We've actually had children ask their parents to stop the reunification process because they're worried that they'll get detained.”

The Department of Homeland Security, which oversees ICE, did not confirm the existence of Operation Guardian Trace or respond to questions about how it’s being carried out.

Here’s what else we know:

How does Operation Guardian Trace work?

Attorneys and advocates who spoke with The California Newsroom say it’s a classic bait and switch.

Laura Diamond, an attorney with the Immigrant Center for Women and Children in Los Angeles, said that in September, an ICE agent asked one of her clients to come to the agency’s downtown L.A. field office with her passport and her teenage son’s birth certificate as part of the sponsor vetting process. The woman had already submitted to a DNA test to prove she was his mother, and had been fingerprinted for a background check, which showed no criminal history. She was fearful because she knew ICE was arresting immigrants, but she went to the office anyway.

“Wanting to do what she was told she needed to do to get her child,” Diamond said, “she showed up, and they arrested her.” The woman, who Diamond declined to name because her deportation case is ongoing, is still in an ICE detention facility. Her sponsorship application was canceled, and her son is now in foster care.

A DHS form documenting her arrest, reviewed by The California Newsroom, says the woman was detained “pursuant to a targeted enforcement operation.”

Three months later and eight hundred miles away in Texas, a similar form buried in a similar case also mentioned an operation, this time by name: “Operation Guardian Trace.”

In that case, a Venezuelan man with no criminal history was arrested while applying to sponsor his two teenage children, who were in ORR custody, according to his attorney, Chiqui Sanchez Kennedy of the Galveston-Houston Immigrant Representation Project. “He got a call on a Friday, ‘Come to the ICE office on Monday,’” she said. “He was specifically told, ‘This could help you get your kids out.’” Instead, the man was arrested and detained for three months in an ICE facility in El Paso. He was released under a judicial order this week, but his kids are still in federal custody.

Through her petition to get her client released, Sanchez Kennedy obtained a record of the arrest. The document is not public, but she provided The California Newsroom with a copy, which she redacted to protect the family’s’ privacy.

An immigrant child is overcome with emotion after she crossed the Rio Grande with her family from Mexico into the United States in Eagle Pass, Texas.

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“As part of Operation Guardian Trace,” the form reads, “Special Agents are required to interview and investigate sponsors and or guardians/parents. During the process, if the sponsor/guardian/parent is determined to be illegally present in the United States, [authorities] will arrest and initiate administrative removal proceedings for possible reunification.”

The Department of Homeland Security did not respond to questions about the meaning of the terms “possible reunification” and "administrative removal proceedings.” The latter can refer to a process ICE uses to bypass immigration courts and quickly deport migrants who have been convicted of aggravated felonies.

While the document offers limited details about Operation Guardian Trace, Sanchez Kennedy said it’s clear that DHS is systematically using the sponsor vetting process to facilitate immigration arrests. “I thought it was pretty incredible how explicit it is,” she said.

Is the policy legal?

The Department of Homeland Security can, generally speaking, arrest someone who is in the country without authorization. But Wroe, of the National Center for Youth Law, said Operation Guardian Trace likely interferes with the government’s obligations to reunify kids with qualified sponsors. The Office of Refugee Resettlement, she said, “has a legal obligation to try and effectuate releases in a timely manner. Collaborating with DHS in this way arguably interferes with their ability to meet those statutory requirements.”

A spokesperson for the Department of Health and Human Services, which oversees ORR, did not respond to questions about that allegation or about Operation Guardian Trace.

ORR regulations also state that the agency “shall not disqualify potential sponsors based solely on their immigration status and shall not collect information on immigration status of potential sponsors for law enforcement or immigration enforcement related purposes.”

The federal unaccompanied children program was intentionally separated from the government’s immigration enforcement agencies through the Homeland Security Act of 2002, which placed the program under the purview of the Department of Health and Human Services. The goal was to focus on child welfare rather than detention.

Donovan-Kaloust said that by cooperating with DHS, the Office of Refugee Resettlement is turning itself into “a quasi immigration enforcement agency, which is contrary to its mandate.”

What’s happening to the kids who are affected?

Many of the detained children Donovan-Kaloust’s team represents in Southern California broke down in tears when they learned their parents had been arrested, she said.

“They feel like it's their fault that their parent is in this situation, because their parent was trying to reunify with them,” she said. “Those are the things that the children are expressing to us. Sadness, hopelessness, tearfulness and guilt.”

According to Ryan Matlow, a child clinical psychologist who contributed to a report last year by the National Center for Youth Law about changes in ORR policy, prolonged detention breaks down children’s natural resilience. “As children come to see that they have no opportunity for release or family reunification,” he wrote, “they are likely to become increasingly despondent, desperate, hopeless, and depressed or agitated.”

Donovan-Kaloust said that in some cases, after her clients’ parents have been deported, the children decide to return to their home country. One boy didn’t want to go, she said, “but it was his only way to be with his dad.”

Like all of the immigration attorneys and immigrant rights advocates we spoke with, Donovan-Kaloust believes self-deportations are part of the point of Operation Guardian Trace.

“The administration wants the immigrant community to give up and go home,” she said. “And this is one way to do it.”

Mark Betancourt is a freelance journalist based in Washington, D.C.

This story was produced with The California Newsroom, a collaborative of public media outlets around the state that includes LAist.

When Sarah Lindbo's 14-year-old daughter Greta is thriving, she is playful, engaged and not in pain.

Greta, who has cerebral palsy, requires a range of supports to get to that point. That includes doctors, medical equipment, prescriptions, a paraprofessional at school and a care assistant at home. Many of these services depend on Medicaid.

" Medicaid makes a huge impact in our day-to-day life," Lindbo said. "It is the foundation of what gives Greta her experience at school and in our community and our family."

But lately, Lindbo has been nervous. She and her family live in Minnesota where hundreds of millions of dollars — and possibly billions — for the state's Medicaid program are in limbo as part of the Trump administration's crackdown on fraud. It came after federal prosecutors last year alleged that billions may have been stolen from Minnesota's Medicaid program over the years and charged a number of people with Medicaid fraud.

Dr. Mehmet Oz, who oversees the Centers for Medicare and Medicaid Services, has argued that widespread fraud has persisted for too long, hurting both taxpayers and those who rely most on the program.

"This is not a problem with the people of Minnesota. It's a problem with the leadership of Minnesota and other states who do not take Medicaid preservation seriously," he said at a press conference on Feb. 25.

But health care policy experts say the threats to Medicaid funding are unprecedented — going far beyond the typical steps to address fraud and at a scale that could disrupt services for patients.

"If this becomes the framework for addressing fraud, it's really destabilizing," said Allie Gardner, a health policy researcher at the Center on Budget and Policy Priorities, a progressive think tank. " It risks the coverage and care for those that depend on the program."

CMS declined to comment, citing pending litigation. Earlier this month, Minnesota filed a federal lawsuit over a portion of the frozen Medicaid funds. In a press release announcing the suit, Minnesota Attorney General Keith Ellison asserted that the state has taken a concerted effort against fraud and the federal government's "cut first" approach risks care for Minnesotans. 

"The Trump Administration's M.O. is to cut first, no matter what the law says or who gets hurt, and ask questions later, if at all," he said.

Breaking down what's happening to Minnesota's Medicaid funds

Administrator for the Centers for Medicare & Medicaid Services Dr. Mehmet Oz speaks during a news conference on efforts to combat fraud, at the White House on Feb. 25, 2026.

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The federal government partners with states to fund Medicaid. But after widespread fraud allegations surfaced in Minnesota, CMS announced it would halt federal funds for the state's program in two ways — retroactively and going forward.

The retroactive move is called deferral. In February, CMS said it would delay reimbursing about $259.5 million that the state spent on Medicaid last summer, citing concerns about potential fraud and coverage for patients without legal status, who are not eligible for Medicaid.

The federal agency asked the state to prove that funds were spent lawfully across 14 categories of providers which Minnesota had previously identified as "high risk" for fraud. (Last year, the state shut down one of the programs, Housing Stabilization Services, citing widespread fraud.)

Deferrals are a standard oversight tool for CMS but they are typically narrow in scope — like a review of a specific set of claims, according to Gardner. When deferrals are too broad or vague, it can be more difficult and time-consuming for the state to gather the proper evidence and respond to the issues, she said.

"The state kind of has to shoot in the dark in responding to CMS on what documentation they need to provide," Gardner said. "What is the scope of information needed? Do they need documentation to justify every single claim?"

The second move is known as withholding. Here, the federal government is saying it will hold off payments for future care.

That decision came after CMS asked Minnesota in December for a plan on how it will prevent future fraud. The state later submitted a proposal with a list of actions, including strengthening certain review processes and pausing provider enrollment in the "high risk" programs. But in January, Dr. Oz announced that the state's plan was "deeply insufficient," and therefore, CMS intended to withhold about $2 billion annually in future federal funding.

According to Gardner, this kind of move is rare, especially with an amount this large. Using both deferral and withholding simultaneously puts Minnesota at risk of a massive and sudden financial hit.

" CMS' use of both of these processes to go after the same services at the same time — that's really concerning," she said. "Especially given the significant financial consequences to the state and providers as well as, to the care and coverage of Medicaid enrollees."

Before CMS can start withholding future funds, the state has an opportunity for a hearing. If CMS decides not to release the funds in deferral, the state also has a chance to appeal. Minnesota's lawsuit pertains to a bulk of the money stuck in deferral.

Minnesota could be a test case for other states

Attorneys representing CMS have argued the $259.5 million in deferral involves services that were already paid for by the state, which only represent about 7% of quarterly federal funds owed to Minnesota.

But Andy Schneider, a Medicaid policy expert with the Georgetown Center for Children and Families, said the state likely planned its budget with the expectation of receiving those reimbursement funds.

" The federal government has just told the state, you have $259 million less to work with for the services that are happening now," he said. "That's a lot in a short period of time."

The potential loss of $2 billion in future funding would be even more challenging for the state to manage, according to Schneider. It could slow payments to providers and delay the enrollment of new patients. It could also force the state to cut reimbursement rates and limit the number of services it covers, he added.

While Minnesota has been under unique federal pressure, CMS has also sent letters to California, New York and Maine, raising concerns about potential fraud in each of the state's Medicaid programs.

Schneider, who also served as a senior adviser to CMS during the Obama administration, said this step could be an early warning signal for deferring or withholding federal Medicaid funding in those states.

Earlier this month, the House Committee on Energy and Commerce launched investigations over Medicaid fraud in 10 states: California, Colorado, Massachusetts, Maine, Nebraska, New York, Oregon, Pennsylvania, Vermont and Washington. All but Nebraska and Vermont are led by Democratic governors.

Schneider agrees that it's important to root out bad actors exploiting Medicaid, but he argues that federal-state collaboration is essential to tackling fraud concerns while not jeopardizing people's access to care.

" If they were really worried about it, they would continue to do what we did in the past, which is to work cooperatively with the state," he said.

When Lindbo first heard about the potential threats to Medicaid, she got emotional. Although her family has private health insurance, Lindbo said it does not cover many of her daughter's critical services, such as the school paraprofessional who helps Greta get ready for class and assists Greta if she has a seizure.

According to Lindbo, any disruption to Greta's care could undo the progress she has made.

" Regression is real," she said. "That would just be so heartbreaking because she's worked really hard. People who work with her work really hard and those systems need to stay in place so she can continue to grow."
Copyright 2026 NPR

After a delay that has threatened plans for World Cup celebrations across the U.S., the federal government said this week that it's moving forward with awarding host cities including Los Angeles hundreds of millions of dollars in funding for security.

Host cities have been counting on the $625 million in federal funds, which were already allocated in last year's "One Big Beautiful Bill" for security costs related to putting on the global tournament.

L.A. will host eight matches at SoFi Stadium in Inglewood, a five-day fan festival at the Coliseum and watch parties and fan zones around the region – and those events will require additional police and resources to pull off.

FEMA, the Federal Emergency Management Agency, is responsible for allocating the funding to the 11 host city committees in the U.S. Last month, officials in Miami and Kansas City raised the alarm that they may need to cancel fan plans if the money didn't come through soon. Los Angeles officials declined to weigh in at the time.

In a statement provided to LAist, FEMA blamed the ongoing government shutdown of the Department of Homeland Security for the delay.

"While the recent funding lapse temporarily slowed the grant process and impacted FEMA’s grants management system, DHS and FEMA have completed their review and approval of applications" the statement said. "Grants supporting host jurisdictions and security efforts will begin going out soon.”

But the saga's not over yet. Los Angeles and the Bay Area are still waiting on those grants, according to a statement from the California Governor's Office of Emergency Services, which is responsible for disbursing federal funds to the World Cup host committees in the state.

The money will be paid out as reimbursements – but organizers can't make plans to use the funds until they know what they've been awarded.

“Cal OES will continue pressing the federal government to announce the World Cup Grant Program awards so host city communities can plan responsibly and ensure the security resources needed for a global event like the World Cup are in place," a CalOES spokesperson told LAist via email.

LAist has asked FEMA, Cal OES and the L.A. host committee how much money they requested for security costs in Los Angeles, but has not received a response.

It's less than three months until the first World Cup match in the U.S. will kick off in Los Angeles on June 12.