Quick Take
January marked the coldest January in the contiguous United States in decades, mostly due to a distorted polar vortex that brought colder weather down from the Arctic. However, it was more of the same in Santa Cruz County, with temperatures largely mirroring those of past Januarys. Still, the vortex can and has brought cold, wet weather to the region, including this month’s atmospheric river.
As the rest of the world saw the warmest January on record, the United States was a noticeable outlier. In fact, the contiguous U.S. actually experienced its coldest January since 1988, thanks in large part to an unusually acting polar vortex, which has sent cold Arctic air southward.
“It’s not something new. Climatologists have watched this for decades,” said National Weather Service meteorologist Brian Garcia. “This year, it’s really set up over the center part of the U.S.”
Polar vortex refers to a broad region of cold, rotating air that forms during the fall when Arctic temperatures cool quickly. Usually, the winds associated with this system tend to remain in the Arctic regions, but sometimes, including this year, the vortex can distort and the cold air can dip into more southerly regions, like the United States. Garcia calls this “Arctic oscillation.”
Garcia said the oscillation can shift between a positive and negative phase. When it’s in the negative phase — when polar winds are weaker — that cold weather is more likely to come down into the U.S., causing a harsh winter.
So, has the frigid winter gripped Santa Cruz County, too? Not so much, said Garcia. He said the NWS weather station at Watsonville Municipal Airport, the only one in Santa Cruz County, showed January’s average temperature was 50.1 degrees, just 0.6 degrees cooler than the average January temperature of 50.7 degrees since 1945.
However, Garcia said that the Arctic oscillation has hovered over Santa Cruz County at times this winter. He said the atmospheric river that drenched the better part of the Bay Area earlier in February is a good example of how the Arctic oscillation can cause tangible weather changes. In this case, it can bring in moisture from the subtropics along with colder, volatile weather.
Garcia also said that it’s a La Niña year, albeit a weak one. La Niña has an opposite effect to its El Niño counterpart, bringing colder surface water temperatures to the West Coast and producing typically drier, warmer conditions in the southern United States and wetter, colder conditions to the north, particularly the Pacific Northwest. Being right in the middle of those regions, predicting the pattern’s effect on Santa Cruz County is always a toss-up. This year, Santa Cruz has been in the drier part of the country.
“The dividing line this year is pretty much at the Bay Bridge. Once you go north of the bridge, they are well over 100% of their average for precipitation, and for us on the Central Coast, we’re below 100%,” he said, explaining that the pattern can interact with Arctic oscillation, bringing cold, wet, stormy weather. “One does not cause the other, but they can amplify each other.”
The next few days will bring some larger waves than normal, said NWS meteorologist Roger Gass, noting that from about 5 a.m. Tuesday until early morning Wednesday, Santa Cruz might see waves of about 10 feet or so. That isn’t as big as the 15- to 18-foot waves expected on west-facing beaches throughout the Bay Area, but they will still bring the risk for rip current and sneaker waves — large waves that typically appear unexpectedly following periods of calm waters. They could occur within 10 to 20 minutes of each other, and have the potential to sweep swimmers, beachgoers and others into hazardous waters.
“I would recommend inexperienced swimmers stay out of the water, and our ocean waters are still very cold, so I wouldn’t advise anyone going in without a wetsuit,” said Gass.
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