California's rainfall year ended today (June 30), and though the totals are not yet official, the parched state will likely end up with one of its lowest rainfall years since the 1920s.
California's precipitation year runs from July 1 through June 30, to account for the fact that most of California's rain and snow falls in the winter months. (Confusingly, there's also a separate "water year," which runs from Oct. 1 to May 31.) When the rain meter ticked over last night, the most recent total was 49 percent of the historical average, according to the state's Department of Water Resources. Rainfall totals have been tracked since the 1850s.
This year's dry spell can be partly linked to a stubborn high-pressure system sitting off California's shores, nicknamed the "ridiculously resilient ridge." This high-pressure ridge acted like a roadblock for winter storms that typically deliver California's rain and snow. The high pressure steered east-flowing storms north, toward the Pacific Northwest, instead of allowing tropical moisture to crash into California's mountains.
The same high-pressure ridge has also sent temperatures soaring, with California sweating through its hottest year on record. January through May 2014 was the hottest string of months in that state since 1895, according to the National Climatic Data Center.
This year is the third consecutive below-normal water year for California. California Gov. Jerry Brown declared a drought emergency for the state on Jan. 17. The entire state is in severe drought conditions, with 77 percent in an extreme drought and 33 percent considered to be in an exceptional drought, according to the National Drought Mitigation Center.
Many communities have ordered water-use restrictions, and farmers are feeling the effects of low water allocations from the state.
The city of Bakersfield, in California's farm-rich Central Valley, received 2.41 inches (6.12 centimeters) of rain, or 37 percent of normal precipitation through June 29, according to the National Weather Service. The same region received 3.15 inches (8 cm) from July 1, 2012, through June 29, 2013, which is 49 percent of normal for the water year.
Here are some of the precipitation totals, as of June 29, from the National Weather Service.
- Los Angeles: 6.08 inches (15.44 cm); 41 percent of average
- Sacramento: 10.35 in (26.29 cm); 51 percent of average
- San Francisco: 12.54 in (31.85 cm); 53 percent of average
- San Diego: 5.06 in (12.85 cm); 49 percent of average
- Fresno: 4.81 in (12.22 cm); 42 percent of average
While an El Niño offers hope of a wet year in Southern California, a moderate or weak event could mean another dry winter in 2014.
Forecasters say there is an 80 percent chance of an El Niño developing by fall, but it's no slam-dunk. This Pacific Ocean climate phenomenon shifts global weather patterns, and often means heavier-than-normal winter rainfall in Southern California. But most of California's winter rainfall occurs in Northern California's Sacramento and San Joaquin river basins, and an El Niño may not bring enough winter rain for the thirsty state to recover from the ongoing drought, water experts say.
In the Sacramento Valley — the state’s largest source of water supply — there’s a 29 percent chance that the 2014-2015 rainfall year will also be critically dry, and a 64 percent chance that it will be a combination of dry or critically dry, according to researchers at the University of California, Davis, Center for Watershed Sciences. Water years are divided into five types, ranging from critically dry to wet.
"Given the odds, it makes sense to prepare for another dry year," the researchers wrote on the center's California Water Blog.