After a relatively dry fall in Southern California, there was a point last December when it seemed as if fears of a strong, wet El Niño winter might be overblown.
So much for this.
Within weeks, a series of powerful storms turned the tide, dropping record-setting torrential rains across California, most of it in the state's southwestern region.
This wet pattern has continued as winter ushers in spring, with last weekend's storm dumping as much as 4 inches of rain in some areas — pushing Los Angeles to a new two-year rainfall total not seen since the late 1800s and dashing any hope For a quick end to the rainy season.
As of Monday morning, downtown Los Angeles had averaged 52.46 inches of rainfall in the last two water years, the second-highest amount in recorded history. The only other period from October to September — the so-called water year — that saw more rain was from 1888 to 1890, according to the National Weather Service.
“When you look at records from 1877 in downtown Los Angeles… [largest total] “It's critical,” said Joe Sirard, a meteorologist with the National Weather Service in Oxnard. “We've obviously been well above normal for two years in a row now. For a dry climate like the Los Angeles area, that's huge.”
And there may be more on the way. A low pressure system is forming off the California coast and is expected to move inland later this week, leading to above-average precipitation forecasts for much of the state through April 10, weather officials said.
Forecasters do not expect this storm to end the rainy season, as the long-range forecast for April calls for slightly above average rainfall in Southern California, according to the Climate Prediction Center.
“We don't think the rainy season is over yet,” said Anthony Artosa, a meteorologist at the National Weather Service's Climate Prediction Center. He said the wetter pattern should continue through April and perhaps into early May, fueled by the last vestiges of El Niño and the Southern Oscillation — the climate pattern in the tropical Pacific that tends to increase wet weather in California.
Monthly rainfall forecast issued on March 31, 2024.
(NOAA)
The current El Niño is shifting to a more neutral pattern, and El Niño is expected to take over by summer, bringing cooler, drier weather. But because the atmosphere tends to lag behind changes in Pacific surface temperatures, “we're seeing a spillover of those changes,” Artusa said. [El Niño] Impacts until later in April.
In fact, this year's wet winter was in many ways a “keystone” event for El Niño — especially since most of the storms arrived in late winter and lasted into the spring, according to Alexander Gershunov, a research meteorologist at the Scripps Institution of Oceanography at the University of California. San Diego.
“El Niño and La Niña signals typically start — when they start, because that's not always the case — in January, February and March, and that's exactly the part of the year that has been abnormally wet this year,” he said.
However, not all wet weather can be attributed to El Niño. Last year's rainstorms occurred during La Niña, and Gershunov noted that some of the state's wettest years this century occurred during La Niña years, which also included 2011 and 2017.
“In all of these cases, the atmospheric river activity was very strong,” he said. “What we're discovering is that atmospheric rivers don't always dance to our own tune [El Niño]“And they can make or break” a textbook El Niño pattern.
The recent storm over Easter weekend caused some highway flooding, brought brief hail and dropped 2 to 4 inches of rain across the region, with some mountain areas totaling nearly 5 inches, according to the weather service. It was far from the strongest storm of this rainy season, but it still brought impressive rain totals: 2.1 inches in downtown Los Angeles, 4.67 inches in Little Creek, 4.09 near Lynwood, and 3.92 inches in Compton, and 3.54 inches at Stunt Ranch.
The heaviest and most widespread rain fell from late Friday into early Saturday, setting several daily rainfall records for March 30, including in downtown Los Angeles with 1.73 inches, Long Beach with 1.86 inches, and Palmdale with 1.12. inch. Snowfall totals were 22 inches in Green Valley Lake, 14 inches in Snow Valley and 10 inches in Big Bear City, according to the National Weather Service.
However, last month, daily rainfall totals more than doubled from the record set on March 30 when a deadly weather river storm swept through the Southland and much of the Golden State, triggering hundreds of mudslides, major flooding and destruction. This system dumped 4.1 inches of rain on downtown Los Angeles in one day, making February 4 the wettest day in February history.
This system came on the heels of a series of powerful storms that brought heavy rain and severe flooding to some areas. Most notably, in late December, a month's worth of rain fell in less than an hour and drenched Oxnard. Then in January in San Diego, historic rains submerged one-story homes, turning roads into rivers and forcing roofs to be salvaged.
“We have witnessed a number of heavy, high-intensity rains,” Cerar said.
With more rain on the horizon in Southern California, Cerar said he wouldn't be surprised if this two-year period ends up being the wettest in the history of the City of Angels, as the current count is 2 inches short of the all-time record, 54.1 inches, which fell from 1888 to 1890.
“We actually have a very good chance of setting the all-time record,” Cerar said.
Last year became the seventh wettest year in Los Angeles history with 31.07 inches falling from Oct. 1, 2022, through Sept. 30, 2023. Meteorologists with the National Weather Service see the area's normal annual precipitation at 14.25 inches, making the year's total Past more than 200.% of average. With six months to go, this water year has recorded 21.39 inches, currently the 22nd wettest in recorded history.
Gershunov said this year's wet winter could also have broader climate impacts, including potential impacts on the upcoming wildfire season. Mountain and forest ecosystems are likely to see less fire activity because late winter and spring snowpacks tend to melt gradually, promoting wetter soils and less combustible vegetation in the summer.
On the other hand, anomalous precipitation in coastal ecosystems — such as the strong storms this winter and spring in Los Angeles and San Diego — promotes the growth of new grasses and other understory plants that can fuel fires.
“All of this will be dry when the coastal fall wildfire season begins with the onset of the Santa Ana winds next October,” Gershunov said.
While this year appeared to follow the rules of El Niño, he noted that the climate pattern doesn't always live up to the hype, such as the El Niño of 2015-16, which was described as a monster event that eventually led to average rainfall. In california. In fact, when measured statewide, precipitation is hovering around average this year, at 20.9 inches since the start of the water year on Oct. 1, or about 107% of the average for that date, state data show.
With more than 30 million acre-feet of water stored, the state's reserves are 116% of their historical average. Meanwhile, snow density reached 105% of average on April 1, the date when it is usually at its peak.
“It is important to realize that ‘average’ precipitation rarely occurs in California,” Gershunov said. “The hydroclimate in California is variable – we either get dry years or rainy years, and that's pretty normal. It's very unusual to have an average year in terms of rainfall in California.
These fluctuations between wet and dry conditions are expected to worsen as climate change upends traditional patterns in the coming years and decades. Indeed, global warming is contributing to shrinking snowpack in part because warmer storms fall as rain instead of snow.
“We could still see very heavy snow years like last year, which had many cold winter storms,” Gershunov said. “But those years are expected to become less frequent.”
