Saturday, April 13, 2024

California is waterlogged after another soggy atmospheric river – The Washington Post

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A seemingly incessant barrage of atmospheric rivers continues to overwhelm California, dumping torrential rains and flooding streets and neighborhoods. Several meters of snow fell in the Sierra Nevada this week alone, with months of rain falling since the beginning of February at the lower elevations.

Flash flood warnings were in effect for Los Angeles Wednesday morning and San Francisco Tuesday afternoon. As the rains eased by midday Wednesday, a few showers still fell on the shore.

Wednesday morning, All lanes of Pacific Coast Highway closed in Malibu due to mudslides, and a section of the 105 Freeway in Los Angeles was flooded. In the Bay Area, a vehicle got stuck in floodwaters in Lafayette Tuesday afternoon, just east of San Francisco, while water flowed from manholes in the city center.

It was an exceptional and, in some cases, record-breaking start to the year in terms of precipitation in California. Back-to-back rainy winters have entirely eradicated a years-long drought that once plagued the Golden State. A year ago, 84.6 percent of California faced some level of drought; according to the US Drought Monitor, this figure is now zero.

How much rain fell?

Downtown Los Angeles has already received 12.56 inches of rain so far this month, the fourth most on record and more than three times the February average of 3.48 inches.

“This is the wettest month in 26 years,” the National Weather Service said in a statement.

The city needs just over an inch to break the February record set in 1998 – with records dating back to the 1870s. With another atmospheric river arriving early next week, the record is threatened.

The 7.03 inches that fell on Feb. 4-5 also represented the third wettest two-day period on record. It falls just below the 7.98 inches that fell on New Year’s Eve and New Year’s Day 1934.

A different rain gauge on the University of California, Los Angeles campus recorded 12.46 inches of rain in 24 hours during the Feb. 4-5 event, which has a probability of only 0.01 percent of occurring in a given year.

Since Jan. 1, 14.38 inches of rain have fallen, the eighth most in 147 years of data and placing it in the 94th percentile.

“Precipitation totals for the 2023-2024 water year now stand at 17.79 inches, about 8 inches above normal to date, and more than 3.5 inches above normal for the entire year,” the weather service wrote.

Sacramento saw 8.02 inches this year, a far cry from the 18.1 that fell at this time in 2017. This year’s total is actually only a few inches above the 6.03 average.

Sacramento had normal rainfall in January, but it was about 2 inches ahead of the February average. The wettest level so far this year was last Sunday, when 1.14 inches of rain fell.

The Bay Area is 2.85 inches above average for the year to date. There were no true record-breaking rain days, but rather a series of days with moderate, steady precipitation that accumulated over time.

So far this year, 9.32 inches of rain has fallen, well below the 1998 record, when 20 inches fell during the same period.

The Central Sierra Snow Lab in Donner Pass, operated by the University of California, Berkeley, has recorded 211.42 inches of snow so far this season and 43.7 inches over the past week. The resort is located near the ski resorts of Lake Tahoe, at approximately 7,000 feet above sea level. So far, its snowfall is within a foot and a half of average for this time of year.

Despite normal snowfall, the central and southern Sierra are 15 to 20 percent behind the amount of water in the current snowpack. The reason doesn’t there was a lack of precipitation, but rather the nature of atmospheric rivers; As they are connected to the tropics, they pump fresh air into the middle layers of the atmosphere, which helps to melt some of the existing snowpack and increase snow levels.

Weather models indicate the next atmospheric river will affect California starting next Sunday or Monday. Subsequently, the National Weather Service’s Climate Prediction Center projects that above-average precipitation chances will last through March along the West Coast.


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