MICHEL MARTIN, HOST:
California is getting walloped by a major, and according to the National Weather Service, extremely dangerous winter storm. Millions of people from Santa Barbara to Los Angeles have been under flash flood warnings. Among them is NPR climate correspondent Nathan Rott, who is with us now from Ventura, Calif. Good morning, Nate.
NATHAN ROTT, BYLINE: Hey, Michel. Good morning.
MARTIN: It sounds like it's been a pretty hectic 24 hours there.
ROTT: Yeah, I'd say that's fair to say. You know, it started raining where I am yesterday a little before noon, and it pretty much has not stopped since. So I've seen some localized flooding here in Ventura, an area near the Ventura River, which is just broiling and brown with runoff right now. There's been flash flooding, river flooding, road flooding, freeway flooding, urban flooding - pretty much any flooding you can think of, Michel, it is happening from Santa Barbara to Los Angeles counties. Further north, there have been hurricane-force winds that have toppled trees and caused nearly a million homes to lose power at one point on Sunday. And then there's more rain in the forecast. So this is very far from over.
MARTIN: So how much longer is this storm expected to last?
ROTT: So until Tuesday at least where I am. This storm is what we call a major atmospheric river. So think of a river of moisture in the sky that's transporting water vapor from the warmer tropics out in the Pacific. And when that river of moisture in the air hits mountain ranges, like the kind that exists pretty much all across Southern California, it forces that air up, and it turns the moisture into rain or snow. So Daniel Swain, a climate scientist at the University of California, Los Angeles, said, right now, those mountain ranges in Southern California are essentially acting like a big catcher's mitt for all of that moisture, which is totally, totally normal, Michel. What's not normal is how fast this atmospheric river is moving.
DANIEL SWAIN: If this was twice as intense - it was moving through four times faster - I don't think we'd be seeing big problems. But this is the big concern. It is slow-moving. It is stalling out. And it looks like it's really going to continue to remain stalled out over this region for a while.
ROTT: And what that means is more rain on already swollen watersheds, already saturated ground, which just means a greater likelihood of flooding and debris flows.
MARTIN: Can you give us a sense of what this means for Southern California residents like you over the next few days?
ROTT: Yeah, well, it certainly means a lot of people are going to have a very uncomfortable Monday morning commute if they're still planning to go to work or school. The National Weather Service is urging people to stay home, but a big thing to keep an eye on because of the sheer amount of water that's falling - and you know, in some places we've seen rates of an inch per hour - is the potential for some kind of major debris flow, a mud flow, through a populated area. That's especially a concern of places that have had wildfires in recent years and in tight canyons, which is why officials have given evacuation orders in a handful of high-risk areas. There's been some reports in the Hollywood Hills and along the Santa Monica mountains that there's some debris flows have happened. The weather service is calling this an extremely, extremely dangerous situation.
MARTIN: And Nate, you cover climate change, where you continue to see these climate-driven disasters every year. This is always the question, though - is this one of them?
ROTT: You know, I talked to a number of climate scientists who study atmospheric rivers over the years. And basically the general consensus is that, yes, at some point, scientists expect to see atmospheric rivers get more intense because of human-caused climate change. They have not detected that yet, though. So at some point, yes - not yet that they've seen.
MARTIN: That is NPR's Nathan Rott in Ventura, Calif. Nathan, stay safe.
ROTT: Thank you, Michel. Transcript provided by NPR, Copyright NPR.
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