When a violent early-season storm flooded parts of Northern California last month, some experts said it happened just in time.
The reservoir levels were critically low. The soils are dry. Fires raged in dry forests.
The general consensus among climate experts is that even a record downpour will not end the two-year drought that has plagued the state. There were too many shortages, and one storm – even of biblical proportions – could not have solved it in one fell swoop.
However, climate experts have expressed hope that the atmospheric river, which washed ashore in late October, could improve drought in parts of Northern California, where rains fell in some areas that broke 100-year records. But that expectation did not extend to Southern California, where only moderate rainfall was received during the storms, and below average rainfall is forecast this winter amid second year of La Niña weather.
While the heavy rains did bring some relief to the northern and central parts of the state – and humidity is expected to be even higher – climate experts and weather officials said it was unclear how long this positive impact would last. They stressed that humidity had little effect on the movement of the larger drought barometer; most of the state continues to experience severe or extreme drought.
“It was a bank account deposit just before it was exceeded,” said Daniel Swain, a climate scientist at the University of California, Los Angeles.
“This does not solve the long-term problem,” he added. California could return to the same boat in a few months when everything dries up, “but it was a significant water injection just in time to help ecosystems weather a fall that would otherwise be difficult to overcome.”
The benefits, ephemeral as they were, were significant.
The dry soil absorbed moisture, and the streams accelerated their pace. Depleted reservoirs began to fill. After an onslaught of fierce fires, the fire season in the northern part of the state was extinguished.
Several northern coastal areas, including parts of Sonoma and Mendocino counties, have gone from extreme drought – the worst category – to extreme drought due to short-term improvements, such as increased soil moisture and river flow, according to Adam Hartman, a meteorologist at National Oceanic. and the Atmospheric Administration and author of the US Drought Monitor. There have also been improvements in parts of Shasta County and northern Sierra Nevada, he said.
By the end of last week, San Francisco and Sacramento had 649% and 675% above average rainfall, respectively, since the beginning of the October 1 water year, according to the National Weather Service. Sacramento reported a record 24-hour rainfall of 5.44 inches during a storm last month, surpassing the mark set in 1880.
However, forecasters in San Francisco and Sacramento are hesitant to do too much about total rainfall given the early season.
As Swain said, “It’s a large number, but it’s skewed by the fact that the denominator is really small.”
The region usually has the highest rainfall from December to March.
“What really matters is how many of these storms do we get by the end of March? There’s a lot of time left until March, ”said Jay Lund, professor of civil engineering and environmental engineering and director of the Center for Watershed Research at the University of California, Davis.
La Niña tends to indicate warmer and drier winters in Southern California, but the relationship between the weather phenomenon and the northern regions of the state is less clear.
While nothing is set in stone, some weather experts are gearing up for a potentially drier-than-normal winter even in the north.
Roger Gass, a meteorologist at the National Meteorological Service’s Monterey office, said forecasts show that rainfall in the Bay Area will be below average. Swain supported this opinion.
While the state’s water year started off with an “active pattern,” that “doesn’t mean we’re not going to dry out during the height of the winter season,” Gass said. “There are still many unknowns.”
A weak storm swept through central and northern California from Friday through Saturday, with a stronger system expected on Monday. Sacramento and San Francisco can get up to half an inch of rain from the stronger system, while coastal ridges and mountainous areas can get up to two inches, forecasters said.
“This is going to happen pretty quickly,” Gass said. “But nevertheless, it will bring healthier and more extensive rainfall to the region.”
There is a relatively small chance that parts of Southern California north of Santa Barbara will experience light rain as the system heads south. Rainfall is likely to be an inch or less, according to Ryan Kittell, a meteorologist at the Oxnard Weather Station.
Unlike Northern California, where rainfall is much higher than average at this time of year, Southern California is “roughly normal,” Kittel said. Approximately three-quarters of an inch has fallen into downtown Los Angeles since the beginning of the year. Typically 0.63 inches of rain falls during this time of the year.
Regardless of how the season unfolds, experts point to alarming long-term dry conditions that will require more than a few storms or even an entire wet winter to wipe them out.
Although many reservoir levels have risen after October rainstorms, Lund said large ones, including Lake Folsom east of Sacramento, remain lower than they were at this time last year.
Bill Patzert, a retired climatologist at NASA’s Jet Propulsion Laboratory, believes it will take 17 years of excess rainfall and snow cover to replenish Lake Mead, an important source of water for the West, which has dropped to critically low levels.
Groundwater levels remain low in other areas as well, said Hartman, a NOAA meteorologist, noting that rainfall “did not seep deep enough into the ground to replenish this groundwater.”
“The long-term effects of the drought are still felt,” he said.