Will the atmospheric rivers drenching California beat back devastating drought? "It's very unpredictable."

Extreme weather is lashing California with torrential rain and snow — the latest in a series of storms going back to New Year's Eve that are known as "atmospheric rivers." The long, narrow bands of moisture from the tropics have dumped days of deluge in the West and can carry up to 15 times the volume of the Mississippi River in each storm system.

Atmospheric rivers are very important — "the main source for moisture for the western part of the U.S., especially the coastal states," said Alex Hall, director of the Center for Climate Science at UCLA.

But the deluge may not be enough to beat back California's devastating drought.

"We are getting exactly what we need to bust the drought, but we still have two-thirds of the wet season to come and we could get very little precipitation," said Hall. "You know, it's very unpredictable."

Scientists say climate change is making extremes more extreme. Droughts are drier and these sorts of winter storms are wetter because a warmer atmosphere holds more moisture.

So when it rains, it pours. That's refilling California's critically low reservoirs and piling up snowpack in the Sierra, which is now more than 200% of normal.

"Our snowpack is actually off to one of its best starts in the past 40 years," said Sean de Guzman of the California Department of Water Resources.

But in Los Angeles, which imports more than half its water supply from Northern California and the drought-ravaged Colorado River, all the rain is a torrent of wasted opportunity. Most of the area's storm water is funneled into the concrete-lined Los Angeles River and flushed into the ocean — an effort to prevent flooding L.A.'s prized possession: real estate.

"We capture about 20% of our storm water," said Bruce Reznik, executive director of LA Waterkeeper, an organization that serves as L.A.'s "water watchdog."

"Between the storm last week and the storm that's happening now, I bet we're gonna see 20, 25, 30 billion gallons of water just going out the L.A. River into the ocean," he said.

L.A. County is spending nearly $300 million a year to capture more storm water, including so-called spreading grounds where runoff can seep into the soil — helpful during the prolonged drought.