City of Berkeley sewer crews clear a drain at Hearst Avenue and Milvia Street, Jan. 4, 2023. Credit: Kelly Sullivan

Brace yourselves, Berkeleyans: Additional atmospheric rivers are on their way.

One storm is expected to drop between 1-2 inches of rain on Berkeley starting Saturday morning and stretching into the evening, bringing with it wind gusts of up to 40 mph, according to the National Weather Service. 

Another stronger storm will likely arrive Sunday evening and last through Tuesday afternoon, dumping between 3-5 inches of rain on the Berkeley flats and closer to 5 inches in the hills. Those totals would make it more similar to the New Year’s Eve storm, which dropped over 4 inches on Berkeley, than the Wednesday-Thursday storm this week, which released around 2.5 inches.

It’ll remain breezy throughout the weekend and early next week, but the strongest winds will likely come Monday, with gusts of up to 50 mph in Berkeley. “The heaviest rain will occur between 4 am and 4 pm Monday,” the NWS said Sunday morning. According to the Global Forecast System, the Bay Area should expect at least two more weeks of rainstorms.

Berkeley was shielded from the worst impacts of this week’s storm (which killed two people, including a Sonoma County toddler, and caused severe damage to some California coastal towns), but that won’t necessarily remain the case for the next two.

The orientation of the coming storms means Berkeley may see more impressive gusts of wind than before, said Brayden Murdock, a NWS meteorologist. “This one is going to filter through the San Bruno gap in a certain way that Berkeley might have more elevated winds.”

The NWS has issued a flood watch in the Bay Area, including Berkeley, from Saturday afternoon through Tuesday afternoon. The agency is warning of widespread flooding, damaging winds, and dangerous beach and marine conditions — the risk of which is heightened because soils are saturated. 

Between Dec. 27 and Jan. 5 a gauge at 800 Bancroft Way measured 10.65 inches in rainfall. That much rain within a 10-day timeframe is expected just once every 25 years for the location, according to NOAA precipitation frequency estimates

It’s shaping up to be an “impressive” wet season, said Murdock. “We’re going to see fairly persistent rain coming for us through the rest of the month, and honestly, if it winds up being a bit more moderate, we’d be comfortable with it. But if they’re aggressive systems, we’re also going to be worried about flooding conditions through a good portion of the month as well.”

Alison Bridger, a professor of atmospheric science at San Jose State University, noted that the current pattern of the rains, with big storms for half a day suspended by a half day of inactivity, could tamp down the flooding risk somewhat. Cities can absorb the rain, let it drain away, and then get ready to receive more. 

A deluge of water floods the streets of North Berkeley, Jan. 4, 2023. Credit: Kelly Sullivan

Alameda County remains in severe drought, though after this week’s rainfall there is no longer anywhere in the state in exceptional drought.

“This is really going to help a lot with the short-term drought in Northern California, and perhaps even erase short-term drought conditions,” UCLA climate scientist Daniel Swain said earlier this week. “But it’s going to take a lot more to completely obviate the longer-term, multi-year drought impacts.”

Scientists will know by April 2023 if this water year’s snowpack is enough to replenish parched reservoirs. The Shasta reservoir is still low, at about 34% of its capacity, while Lake Oroville is at 39%. 

The Bay Area was on the edge of the storm this week

According to Bridger, the storm on Wednesday and Thursday resulted from a combination of unusual weather systems. Mainly, a cold front and a low-pressure front that were much stronger than usual. Cold fronts are the leading edge of a mass of cold air. They’re like a giant moving wall that pushes into warmer air, which has low-pressure, eventually raising the warmer air higher up into the atmosphere. This creates heavy wind, rain, and sometimes thunderstorms.

Bridger said that while it was important for people to prepare for a strong storm, it was always likely that the Bay Area was only going to be touched by its edge, where wind and rain levels were lower. Had the center of the storm passed over the Bay Area, the effects would have been more destructive. 

The Aquatic Park lake overflows its boundaries in the rain on Jan. 4, 2023. Credit: Kelly Sullivan

Bridger said the Bay Area is in general less likely to suffer from devastating rains due to its location. Most storms typically make landfall further north. “When big weather systems come to us, they come close but usually move eastward and then wash ashore north of California into Oregon, Alaska, and British Columbia. We are on the margins of [those big systems.]” 

Climate experts say changes to the jetstreams that move air in the atmosphere are the main reason we are experiencing stronger storms right now. 

Jetstreams are bands of air currents that move across the globe eastward, in a zig-zag motion, and carry storms from the ocean onto the land, usually eight to 10 kilometers above the ground. Normally, the jetstream over Northern California moves air and water moisture from north to south, but right now, it’s reoriented in a more direct west-to-east direction, putting the Bay Area in the storm’s crosshairs for hours at a time. 

A ‘bomb cyclone’ is not a cyclone. But it is likely a consequence of global warming

Dan McEvoy, an associate research professor of climatology at the Desert Research Institute, said he believes that the media, particularly TV news, did not do a good job explaining what a bomb cyclone actually is, and this led to some unnecessarily hysterical reactions. 

“That terminology leads to some ideas of a more powerful storm system,” he said.

A bomb cyclone, McEvoy explained, only refers to how quickly the cold, low pressure strengthens within a storm’s center. When mentioned on TV without context, McEvoy and Bridger both said, it could have led viewers to believe the storm had the power of a cyclone, which it never did. 

“There were a lot of satellite images of this really big storm that [can be misinterpreted],” McEvoy told us. 

Focusing on the potential consequences of a bomb cyclone can be difficult enough to deal with without this misunderstanding, particularly in regions with poor maintenance and infrastructure. For example, McEvoy said that this storm system hit the mountainous regions of Santa Cruz as well as coastal areas especially hard. “What really matters is the impact related to the flooding, the rain, the winds, and of course, the mountain snowfall,” he said.

The role that global warming plays in causing higher levels of rain also needs to be better understood, experts said.

According to Bridger, there is no doubt atmospheric moisture is increasing as the planet warms, producing storms with more rain. If the most recent storm had occurred 30 years ago, she said, it probably would not have produced the levels of rainfall we saw this week. 

How to prepare for a storm in Berkeley

City workers load sandbags into Berkeley residents’ cars Tuesday afternoon before the atmospheric river storm. Public works staffer Rigoberto Marquez (left) said there was more demand for sandbags Tuesday than he could remember in his 14-year career. Credit: Zac Farber

Berkeley  recommends residents protect their homes and businesses from flooding by clearing storm drains, cleaning gutters and downspouts. 

Volunteers with Berkeley’s adopt-a-drain program have access to the city’s reflective vests and garbage bags; there are currently around 30 storm drain volunteers, with new applications still being screened, albeit slowly due to staff vacancies. 

The city is operating an emergency shelter at the North Berkeley Senior Center (1901 Hearst Ave.).

Residents and businesses can call 311 (or 510-981-2489 after hours) to report storm-related issues “such as a clogged drain, culvert, inlet, or creek; a fallen tree or major limb; a malfunctioning traffic signal; or flooding that enters a travel lane.” If there’s a public works emergency, such as a toxic spill or sewer overflow, you can call 510-981-6620.

Severe storms often cause flooding in intersections and roadways in Berkeley. If you encounter a flooded road while driving, the city wants you to “turn around, don’t drown.” 

Berkeley residents can take sandbags for free from the city’s Corporation Yard at 1326 Allston Way on weekdays from 8 a.m. to 4 p.m.

Read more about storm preparation on the city website.

This story was updated after publication.

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Iris Kwok covers the environment for Berkeleyside through a partnership with Report for America. A former music journalist, her work has appeared in the San Francisco Chronicle, KQED, San Francisco Examiner...

Jose Fermoso reports on traffic and road safety for our sister site The Oaklandside.