BERKELEY, Calif. (KRON) -- Winter is coming. Will this winter's snow and rain save California from its severe drought? To get a sense of how possible that outcome is, we first have to figure out how much we need.
"That is the magic question," said Andrew Schwartz, lead scientist of UC Berkeley's Central Sierra Snow Laboratory. The answer depends on which snowpack you're looking at.
"California's snowpack varies from place to place. I can really only speak to what we would need at the snow lab. At this point last year, we needed approximately 140% of our precipitation to come out of the drought. That would mean 42 feet of snow for us here at the snow lab, rather than our average 36 feet," Schwartz told KRON4 Friday.
In all likelihood, Mother Nature will have to deliver abnormally wet weather over multiple winters before the drought will disappear.
"It's quite unlikely that a single winter/year will provide enough precipitation to resolve the drought -- even temporarily. We really need a few successive years of above-average rain and snowfall," Schwartz said.
In April, when the snowpack is usually deepest, it measured 38% of average statewide, according to the California Department of Water Resources.
When a drought lasts as long as California's current dry spell, it takes even more precipitation to escape from it, Schwartz explained.
"Due to the compounding effects of this multi-year drought, we likely need closer to 150% - 175% of our average annual precipitation, which would come out to a whopping 54 feet to 63 feet of snowfall," Schwartz said.
Located at Donner Pass in the Sierra Nevada, the Central Sierra Snow Laboratory is a research field station specializing in snow physics, snow hydrology, and meteorology.
As one of the best-instrumented snow study sites in the world, CSSL has been recording and studying snowfall since the lab was built in 1946. Looking at historical data, what are the chances of between 54-63 feet of snow falling before winter is over?
Schwartz said it's not impossible, but researchers have only recorded more than 50 feet falling four times in the last 40 years. More than 54 feet of snow fell just twice within the past 70 winters.
The long-range forecast for this winter does not look promising. "The forecasts that we've examined show warmer and drier than average conditions, so it's unlikely that we'll see a drought recovery year from the upcoming winter. We might get the occasional big storm, but the winter is supposed to be relatively drier overall," Schwartz said.
Forecasts can change in any given winter, of course. Daniel Swain, a climate scientist with UCLA told Cal Matters that we could get lucky, depending on the path of storms.
However, Swain said, "I would still put my money on dry, even in the northern third of the state."
La Niña can move the winter storm track that California depends on for rain and snow.
The Northern Hemisphere's current La Niña is a "triple-dip," lasting three consecutive winters, according to the Word Meteorological Organization. December, January, and February are typically the wettest months of California’s water year.
La Niña is expected to continue with a 91% chance this September through November, decreasing to a 54% chance in January through March of 2023, according to NOAA.
from KRON4 https://ift.tt/IysEgut
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