'Rivers in the sky' have drenched California, yet even more extreme rains are possible

In California specifically, 44 atmospheric rivers made landfall from October through March, up from 31 during last year’s rainy season, said Chad Hecht, a center meteorologist.

But even though there were more atmospheric rivers this rainy season, fewer of the storms measured strong or extreme on the center’s strength scale compared to the season before that.

“It’s not the quantity, it’s the quality,” Hecht said.

For example, 12 strong, extreme or exceptional atmospheric river storms hit California between October 2022 and March 2023. These heavier storms tend to bring news-making rain and snow. This season, however, the state recorded only five.

“If you compare it to last year, ... this (water) year was a couple of strong storms, but it’s a lot more weaker,” Hecht said. “But the abundance of weak-to-moderate (atmospheric rivers) kind of helped keep us on trajectory to hit that normal (precipitation levels).”

As of this month, records for both statewide precipitation and the snowpack across the Sierra Nevada stood at about 105% of average for this time of year — which Hecht called shockingly close to average.

“This year was abnormally normal,” Hecht said. “We like to talk about California being the land of extremes, where it’s either extremely dry or extremely wet. This year was abnormal because it was fairly close to normal through April 1,” the date that typically marks the end of California’s wet season.

However, Southern California has seen a more anomalous water year, with its yearly rainfall well over 140% of average across many coastal areas, according to the California Water Watch.

Hecht said one strong, slow-moving atmospheric river in early February had an outsized effect on the region’s rainfall, and he noted that many areas were also hit by thunderstorms during what he called “overly productive” weak atmospheric river storms.

The systems aren’t typically accompanied by thunderstorms, but several systems were this season, driving locally historic rainfall and flash flooding in several areas, including San Diego and Oxnard.

...continued

swipe to next page