Much of Northern California has received only two-thirds of its normal rainfall over the past three years, according to Golden Gate Weather Services meteorologist Jan Null.
“It’s like working for three years and only getting paid for two,” he said.
Some places, such as Ukiah, Santa Rosa and Mount Shasta City, are even worse, harvesting about half or less of their normal rainfall.
Null has compiled a summary of the three rainy seasons from July 1, 2019 to June 30, 2022, and the figures clearly illustrate the severity of the drought in the state.
Places in Southern California fared better, with downtown Los Angeles receiving 77% of normal rainfall over a three-year period and San Diego getting 85%. But rainfall in the northern part of the state is more consequential for Southern California and the Golden State’s complex plumbing system than what falls south of the Tehachapi Mountains. Much of California’s significant rainfall occurs in the north. Rainwater and melting snow are captured there in huge reservoirs such as Lake Shasta and Lake Oroville.
Null said, if he could pick a single number to describe the state’s water situation, it would be the Northern Sierra Eight Station Index. What he calls “bellwether” stands at 61% above normal between 2019 and 2022, two-thirds less than expected.
This index is an average of eight rainfall locations that provide a representative sample of the major watersheds north of the Sierra. These basins include the Sacramento, Feather, Yuba, and American Rivers, providing a large portion of the state’s water supply.
And that supply is scarce. According to the U.S. Drought Monitor, most of the state is experiencing the most severe drought, and about half of the state is in extreme drought. Nearly 12% of California is considered to be in an exceptional drought state, the worst of its kind. Since the state’s Mediterranean climate is generally rainy summer months, there is no prospect of immediate relief. Furthermore, the tropical Pacific La Niña climate pattern, which often leads to dry winters in Southern California and the Southwest, is expected to continue into a rare third year.
Rising temperatures and increasingly drier climates due to climate change are increasing droughts during the driest 22-year period in the West in 1,200 years.
December in the state is unusually wet and snowy, but then the shoots die off over the next few months, often the wettest time. According to Null, a river with a strong atmosphere in December made landfall in the state from about Monterey to just north of the Golden Gate, and from about Yosemite to Oroville. But even in that target area, the amount of rain is not much. For example, San Francisco ended the 2021-2022 rainy season with 82% of normal, but for the three-season period ending June 30, it had only 56% of normal.
Places like Ukiah and Mount Shasta City, for example, are not so lucky. According to Null, they end up with 43% and 45% of the three-year norm because they lie north of the December atmospheric river and too far south for hurricanes that wet the far northwest corner of the state, according to Null. Santa Rosa was only 55% above its three-year normal.
The lack of rainfall this year contributes to arid conditions and the arid environment is much more prone to wildfires. The National Interstate Fire Center’s outlook for July calls for an above-normal wildfire potential north of the Interstate 80 corridor. Above-normal potential extends south from there to the Tehachapi Mountains. through the coastal ranges and the central and southern Sierra Nevada.
https://www.latimes.com/california/story/2022-07-07/a-years-worth-of-california-rainfall-has-gone-missing A year’s worth of California rainfall has gone missing