San Diego’s dangerous flash flood on Monday may not be the state’s last such event of the next couple of weeks, as a weather pattern favorable to atmospheric rivers takes shape across the Pacific Ocean.
Why it matters: Atmospheric rivers are responsible for the majority of the Golden State’s precipitation, and are associated with some of its worst floods on record.
Zoom in: On Monday, a relatively weak atmospheric river, along with favorable winds in the mid-to-upper atmosphere, combined to deliver a deluge to San Diego, with the city seeing 2.73 inches of rainfall.
- This ranked as its fourth-wettest day on record, as well as the wettest January day.
- Most of the rain there fell in just a three-hour period and focused on downtown San Diego, a region with poor stormwater runoff issues. This led to severe flooding and more than two-dozen water rescues, as Axios’ Andrew Keatts reports.
In the future, rising greenhouse gas emissions are expected to amp up the frequency, intensity and duration of such atmospheric river “sequences.” These stretches correspond with periods when California faced heightened potential for flooding, according to a new study by scientists from Stanford University and other institutions.
“Sequences are, by definition, capturing these periods of time when we’re close to capacity and more likely to go over that tipping point into damage,” said lead author Corinne Bowers.
The scientists cataloged atmospheric river sequences by looking at weather and climate data corresponding to wet seasons from 1981 to 2021. They pinpointed when specific locations logged consecutive days with high levels of water vapor moving across the sky — a defining feature of atmospheric rivers.
Atmospheric river sequences align with days when California faced extreme precipitation, extreme runoff and extreme soil moisture, the researchers found. These variables are associated with hydrologic hazards, like flooding and related events, including landslides.
California may have endured an onslaught of tropically-infused atmospheric river storms that filled the calendar for months at the end of 2022 and the start of 2023 and is staring at another atmospheric river this weekend, but those storms pale in comparison to the historic floods during the winter of 1861-1862.
–Widespread flooding swamped large stretches of Central California’s valleys. In one stretch of valley that measured about 30 miles wide and 250 miles long, water depths ranged from a few inches to 30 feet in some areas. Telegraph poles were underwater.
“It’s documented that Leland Stanford, newly elected governor of California, was rowed to his inauguration in flooded downtown Sacramento during the floods,” Schick said. “Many wanted to move the capital from Sacramento to San Francisco because of the flooding. Damages to California included losing 25% of its tax base. The state teetered with bankruptcy.”
Southern California wasn’t spared as the relentless storm track moved south into the region in January 1862. The Santa Ana River in Southern California measured water flow on Jan. 22 at 318,000 cubic feet per second – about half the flow of the Mississippi River despite being a tiny fraction of its size.
Most of California is semi-arid. Most of the time people are complaining about no rain. These rains are a good thing…. or would be if California had spent the money on reservoirs and flood control.
This new “research” is just a prediction, which given the record of climate predictions can be safely ignored. Of course, the smart play would be to spend the money to capture and control these series of atmospheric rivers. California is after all a farm state and its biggest issue I would speculate is the lack of fresh water. It’s implausible emissions cause ARs, but even if they did, it wouldn’t be emissions in the US but rather in Asia over which we have no control.
“It’s implausible emissions cause ARs, but even if they did, it wouldn’t be emissions in the US but rather in Asia over which we have no control.” What is your definition of emissions in that statement?
The study claims the emissions cause the ARs. It also claims the ARs come from Asia. I can’t imagine what emissions would do this, but my guess would be GHGs.