Drought? What drought?
Californians could be forgiven for asking that question after two big storms in December brought record rain to the north and mountain snow to Southern California that dusted palm trees in some lower-elevation towns. The start of a new year, however, has the state back in a dry stretch, and experts wonder what's in store for the critical few weeks ahead.
"We must necessarily plan for the worst but hope for the best," said Jeanine Jones, deputy drought manager with the California Department of Water Resources. "We are only now entering the normally wettest part of our winter season, and what happens -- or doesn't -- in the next six weeks or so will tell us a lot about the likely outcome of the water year."
But the start to 2015 does not look promising for the Golden State. On New Year's Eve, the Los Angeles branch of the National Weather Service summarized the outlook on its Facebook page. "Rain for California to bring in the New Year?" it asked. Showing a map modeling precipitation over the next week, its answer was blunt: "Not very likely."
And with California's rainy season being defined by a short winter window, what happens in January and February will be critical.
"A worst-case scenario for us would be a repeat of last year's very dry hydrology -- fourth driest year on record in terms of statewide runoff," said Jones. "A best-case scenario would be a series of storms that provides the snowpack to refill the major reservoirs, but not with a timing that causes flooding problems."
Snowpack typically provides a third of the state's water via reservoirs, but Sierra Nevada levels are just half their long-term average, even with the December storms.
"In the coming weeks we need more snowpack accumulation in the Sierra Nevada and Cascades Ranges to help replenish reservoir storage later in the season," said Jones.
The rains did raise levels at California's largest reservoirs in the north, but basins are also still at just half their average levels for this time of year. Moreover, those farther south "are still woefully short and are not showing the same improvement" as the north, said Mike Anderson, the state's climatologist.
As the state enters a fourth year of drought, a key variable in all this is El Nino -- the periodic warming of Pacific Ocean waters that tends to mean precipitation over California. "El Nino impacts in California usually show up with the new year so we will have to wait and see what happens there," said Anderson.
Experts have been signaling a potential El Nino for months, and one could still develop, but expectations were muted in mid-December when the National Atmospheric and Oceanic Administration (NOAA) said that the Pacific waters were as warm as they were expected to get.
Some scientists also point to manmade greenhouse gas emissions and warmer temperatures as exacerbating drought conditions, especially in naturally dry areas like California and the rest of the U.S. Southwest.
California and Arizona will likely see 2014 go down as their warmest years on record, NOAA says, reflecting high temperatures that dry out soils and melt snowpack faster than a drought would by itself.
"If this winter proves drier than usual" for either California or the greater Southwest, said Jonathan Overpeck, director of the University of Arizona's Institute of the Environment, "then expect much greater pain and recognition of the role that climate change is playing in drying out critical portions of our nation."
"In the greater Southwest, stretching from California east to the High Plains, and north to the border with Canada, we've been in drought since about 1999," he said. California and the Colorado River basin, which supplies water to 40 million people, are "especially on the edge of major pain."
"We are close to a tipping point in both California and the Colorado River Basin," said Overpeck. "A bad winter could quickly accelerate the severity and impact of droughts in these two regions."
Kevin Werner, director for western services at NOAA's National Climatic Data Center, emphasized that point as well at a press briefing last month. California's low reservoirs and the fact that Colorado River flows have been below average for 11 of the past 15 years, he said, "means that this year is pretty critical for water resources" across the Southwest.
And that December rain and snow? "The recent storms have been helpful but we've got a long, long way to go," said Werner at the press conference. "It's going to take a lot of above average precipitation, likely not just this winter but future winters as well."
As for what California will actually get, Jones said, "only Mother Nature knows!"