In six months, L.A. went from high and dry to wet and wild. Here’s how it happened
Since October, downtown L.A. has received more than 13 inches of rain.
At the end of June, Los Angeles had recorded its driest five-year period since record-keeping began almost 140 years ago.
The announcement seemed like an ominous milestone, especially after an El Niño-fueled weather pattern that was supposed to drench the region had failed to materialize.
But just six months later, L.A. has seen a major turnaround.
Los Angeles is experiencing its wettest winter in years, with 14.33 inches of rain since October — more than 200% of average. That’s nearly as much rain as the city gets in a typical year.
So how did Southern California go from high and dry to wet and wild so quickly?
One answer could be that lingering energy from last year’s strong El Niño, combined with not-quite La Niña conditions — which typically foreshadow dry weather in California — helped set the stage for a comeback season, state climatologist Michael Anderson said.
Also a factor is the famous mass of drought-causing high pressure that once shooed winter storms away from California and was called the Ridiculously Resilient Ridge. This year, that mass of high pressure has been much more transient, shuttling between Hawaii, Baja California and California. When it has gone traveling, that’s opened up a path for wet storms to reach California, Anderson said.
“It’s just the right set of circumstances that everything lined up for California,” Anderson said. “If things line up just right, it sets up for conditions for a very wet California.”
That has meant the arrival of both cold storms from the north Pacific Ocean and warmer, subtropical moisture plumes targeting California, a perfect combination that has dumped astonishing levels of snow in the Sierra Nevada — as much as 20 to 30 feet — and dropped impressive rain in Southern California that flooded freeways and triggered mudslides.
In fact, the last rainstorm was a hybrid of both types, UCLA climate scientist Daniel Swain said. The cold, strong storm from the Gulf of Alaska combined with warmer, moister, subtropical air over L.A., which caused hail around the region and heavy, intense rain on the south L.A. County coast. On Sunday, 3.87 inches fell at Long Beach Airport, setting an all-time record for the area.
“It’s not common to see a full day of soaking rain in this part of the world,” Swain said.
What California is actually seeing this winter was what experts had expected last year, as a massive El Niño — a warming of ocean temperatures in the Pacific Ocean — developed.
“We have these very strong west-to-east winds — we call them zonal winds — at the jet stream level in the atmosphere that has sort of propelled this prolonged series of storms toward California … and actually allowed these storms to strengthen,” Swain said. The presence of this strong jet stream is key, Swain said, as California lies in a region in which storms often weaken as they approach the state.
Last year, the strong west-to-east winds over the Pacific Ocean did develop, but instead of being aimed at Southern California, it benefited areas to the north, especially Oregon and Washington. “This year, it really is headed right at us,” Swain said.
A surfer barely clears a giant wave in Manhattan Beach.(Genaro Molina / Los Angeles Times)
People enjoy the snow in Acton.(Michael Owen Baker / For The Times)
Elizabeth Wolterbeek plays among rocks in the 200 block of Mel Canyon Road in Duarte on Friday after a mudslide.(Irfan Khan / Los Angeles Times)
A girl loses control of her umbrella after being rescued by a Huntington Beach police officer and a tow truck operator. Her family became trapped in their disabled car in the middle of flooded Heil Ave. amid a heavy downpour in Huntington Beach.(Allen J. Schaben / Los Angeles Times)
Commuters navigate a rain-soaked 10 Freeway in downtown Los Angeles on Thursday morning, as the first of three storms rolls through Southern California. More storms are expected over the weekend.(Irfan Khan / Los Angeles Times)
Palmdale residents Cesar Navarro, left, and his son Cesar Navarro Jr. sled down a snowy hill in Acton.(Michael Owen Baker / For The Times)
A fast moving discharge of water spews from the San Gabriel Dam, as a storm front moves through the area.(Robert Gauthier / Los Angeles Times)
A bicyclist comes to the end of a trail that’s covered in wet sand at Dockweiler State Beach in Playa del Rey.(Genaro Molina / Los Angeles Times)
Snow covers boat slips and a lone picnic at Lake Arrowhead on Monday as the latest strom moves through.(Gina Ferazzi / Los Angeles Times)
Debris, including drinking cups, rubber balls and bottles, washes ashore along the Alamitos Peninsula near East Ocean Boulevard and 56th Place in Long Beach on Monday.(Mark Boster / Los Angeles Times)
Dale Ball of La Cañada Flintridge has rain gear for herself and her dogs while walking toward the entrance to Hahamongna Watershed Park in Pasadena on Jan. 23.(Mel Melcon / Los Angeles Times)
A car drives through a snowy scene on Shannon Valley Road in Acton.(Michael Owen Baker / For The Times)
A city worker uses a snowblower to clear the walkways during a snowstorm at Lake Arrowhead Village.(Gina Ferazzi / Los Angeles Times)
With the road closed to traffic, Paul Doolin rides a skateboard past a fallen boulder that rests on Topanga Canyon Blvd.(Genaro Molina / Los Angeles Times)
A city worker shovels the walkways during a snowstorm at Lake Arrowhead Village in the San Bernardino mountains.(Gina Ferazzi / Los Angeles Times)
Jose Villa of Lake Arrowhead clears fresh snow off his windshield during a blizzard in Rimforest, Calif.(Gina Ferazzi / Los Angeles Times)
Snow begins to fall and stick to the road in Crestline, Calif.(Gina Ferazzi / Los Angeles Times)
Enrique Nicanor carries plywood on an improvised walkway he made over a flowing creek that damaged the driveway to the house where he works on Iron Canyon Road.(Michael Owen Baker / For The Times)
Clearing storm clouds are reflected in the wet sand at low tide in Newport Beach on Monday.(Mark Boster / Los Angeles Times)
County of Los Angeles pubic works equipment clears the flooded creek on Iron Canyon Road.(Michael Owen Baker / For The Times)
Niklas Hofverberg and his daughter Bianca Hofverberg, 3 1/2 years old, watch the sun set as storms clouds dissipate in Venice on Monday.(Genaro Molina / Los Angeles TImes)
John Fisher of Altadena looks out toward Devils Gate Reservoir in Pasadena on Jan. 23.(Mel Melcon / Los Angeles Times)
Westminster resident Shirley Hansen carries her dog Scruffy while she walks through floodwater caused by recent rain on the boardwalk in Seal Beach.(Mark Boster / Los Angeles Times)
A glimpse of blue sky is seen during a break in the rain at Devil’s Gate Reservoir in Pasadena on Jan. 23.(Mel Melcon / Los Angeles Times)
Gina Picciolo takes a picture of a boulder that fell onto Topanga Canyon Blvd. Picciolo is a longtime resident in the area.(Genaro Molina / Los Angeles Times)
Ward Preston and Gina Picciolo walk past a mudslide along Topanga Canyon Blvd.(Genaro Molina / Los Angeles Times)
A Huntington Beach police officer watches a tow truck operator hook up chains to rescue a family from the middle of flooded Heil Avenue after their car stalled in the deep water amid a heavy downpour in Huntington Beach on Jan. 22.(Allen J. Schaben / Los Angeles Times)
A rainbow appears over Seal Beach, Calif. on Monday. The tail end of a punishing winter storm system lashed California with thunderstorms and severe winds Monday after breaking rainfall records, washing out roads and whipping up enormous waves.(Amy Taxin / Associated Press)
Jerry Katz stands next to a mudflow at the corner of Mel Canyon and Brookridge roads in Duarte.(Genaro Molina / Los Angeles Times)
A Huntington Beach police officer watches a bus drive through flooded Heil Avenue amid a heavy downpour in Huntington Beach.(Allen J. Schaben / Los Angeles Times)
A man looks for a safe way to cross floodwaters flowing from hillsides in a nearby recent burn area on North Iron Canyon Road in Santa Clarita.(Brian van der Brug / Los Angeles Times)
A Huntington Beach police officer diverts a pickup driver while a tow truck operator hooks up chains to rescue a family from the middle of flooded Heil Ave.(Allen J. Schaben / Los Angeles Times)
Mud and rocks have filled the driveway of a Duarte home along Mel Canyon Road, where residents have been evacuated due to mudslides.(Genaro Molina / Los Angeles Times)
Rudy Fuentes stands on the porch of his home on Mel Canyon Road in Duarte, looking out at where mud has taken over his driveway.(Genaro Molina / Los Angeles Times)
Police stop traffic on Mountain Crest Road where residents have been evacuated due to incoming storms in the Fish fire impact area in Duarte.(Genaro Molina / Los Angeles Times)
Marcus Jenkins selling umbrellas as he shelters under one of his own on Hollywood Blvd in Hollywood as the second of three winter storms begin to drench the Southland Friday.(Al Seib / Los Angeles Times)
Motorists navigate the flooded lanes of northbound Fairview Street in Santa Ana.(Mark Boster / Los Angeles Times)
Ella Masa, all wrapped in plastic, pushes her two service dogs as she joins an East LA/Boyle Heights group with banners and posters marching from Mariachi Plaza on Friday, protesting President Trump’s inauguration.(Al Seib / Los Angeles Times)
Umbrellas are necessary on Hollywood Boulevard as the second of three winter storms begins to batter Southern California on Friday morning.(Al Seib / Los Angeles Times)
A pedestrian scurries across the street under her umbrella in downtown Los Angeles on Friday morning.(Irfan Khan / Los Angeles Times)
Paulina Tu takes cover under her umbrella as she waits for a ride in downtown Los Angeles on Friday morning.(Irfan Khan / Los Angeles Times)
With three storms hitting Southern California in five days, there hasn’t been time to dry out between them. “We’ve seen water flowing now in most all of the different streams and larger rivers in Southern California, which is the first in about six years,” National Weather Service meteorologist Eric Boldt said.
Late Monday, Gov. Jerry Brown issued emergency declarations for 50 counties, including Los Angeles, Orange, Ventura, San Bernardino and San Diego. The declarations will help counties speed up applications for state and federal disaster relief funding.
In the past, when there has been no El Niño or La Niña — neither a warming nor a cooling of the Pacific Ocean at the equator — significant rainfall for California can occur. Such “La Nada” conditions were present in the winter of 2004-05, which produced the second-wettest rainy season in downtown L.A. history. Those rains preceded devastating landslides in La Conchita in Ventura County and Bluebird Canyon of Laguna Beach.
“With a La Nada — no El Niño, no La Niña — anything can happen,” said Bill Patzert, climatologist at the Jet Propulsion Laboratory in La Cañada Flintridge. He also noted that the atmospheric river storms are coming from an area of the ocean that has warmer temperatures. “That’s a hangover from El Niño.”
The atmospheric river storms have arrived in a number and size not seen in years, said Marty Ralph, director of the Center for Western Weather and Water Extremes at the UC San Diego Scripps Institution of Oceanography.
Atmospheric rivers are long plumes of concentrated water vapor that are an important feature of the global water cycle. Strong ones can transport as much vapor as equivalent to 20 times the liquid water discharged by the Mississippi River into the Gulf of Mexico at any given moment. Atmospheric rivers are responsible for 40% to 50% of California’s annual precipitation, Ralph said.
“When have a lot of them, sometimes we get into flooding. When we don’t have enough of them, we get into drought,” Ralph said.
The storms have benefited some Southern California reservoirs, with Castaic Lake at about 71% of capacity Monday. Northern California’s windfall has allowed water to flow into Diamond Valley Lake, a critical reserve for Southern California. The giant reservoir is now at 72% of capacity, up from 37% from about a year ago.
But there is still a long way to go before any victory can be declared. Lake Perris is filled to only half of its normal level. Lake Cachuma in Santa Barbara County is still only 13% of its historical average for this time of year.
“While the rain was pretty impressive and welcomed here by everyone watching the skies, it was certainly not enough to end the drought or to fill up the lake significantly,” said David Matson, assistant general manager of the Goleta Water District.
The groundwater supply is also far from recovered. Southern California has been drawing down groundwater reserves during the drought. Parched soils have absorbed much of the water, limiting runoff. And many of the region’s groundwater basins remain severely overdrawn.
“Don’t be mistaken — they are depleted … severely depleted,” said Mark Pestrella, acting director of the L.A. County Department of Public Works. “We are not out of severe drought here in Southern California. We will need three identical years of this type of year to come out of this drought cycle.”
For instance, the Key Well level at the Main San Gabriel Groundwater Basin in Los Angeles County dropped to a historic low of 172.2 feet in October. The historic high was more than 295 feet, achieved in 1983 after one of the wettest winters in recorded California history.
The U.S. Drought Monitor recently revised its map to show no signs of drought conditions in Northern California because of recent rains. The map has been criticized by some experts for oversimplifying the situation in California, who say weekly changes in weather patterns don’t mean the drought is over.
“People are still relying on bottled water in some parts of Tulare County. And some surface reservoirs are remarkably low. These are impacts that can’t be ignored when you’re assessing whether you’re still in a drought,” said Doug Carlson, spokesman for the California Department of Water Resources.
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