Experts: Sonoma County's bone-dry December does not make a drought

A bone-dry December in Santa Rosa and minimal rain anticipated in January may be conjuring up concerns of a renewed drought in a state short on precipitation since fall and with a skimpy Sierra snowpack.

But no worries so far, meteorologists and water managers said Tuesday, citing above-average water supplies in California's major reservoirs and two typically wet winter months ahead.

'I don't think we're near a drought now,' said Jan Null, a consulting meteorologist and former National Weather Service forecaster, even though December has been 'absolutely a bust' for rain. He cautioned that one month hardly makes for an arid season.

Null acknowledged the similarity between current conditions — a persistent high-pressure ridge shunting Pacific Ocean storms to the north — with the official government forecast he wrote in rhyme in February 1977 during a memorable drought:

'Strong high pressure remains firmly entrenched...

Blocking all storms that might leave us drenched.'

Steve Anderson, a weather service meteorologist, said 'only the governor can say the D-word.'

Meteorologist Daniel Swain, who writes the California Weather Blog, said the ridge has forced several atmospheric river storms to 'make a hard left turn' over the ocean, veering north and dumping heavy snowfall on the coastal mountains of southern Alaska.

At the same time, the land-to-sea Santa Ana winds that have propelled Southern California's monster wildfires have blown nearly all the moisture out of the region's air mass, he said.

Most of California has received less than 70 percent of average precipitation since Sept. 25, according to the Western Regional Climate Center's latest report. Virtually all of Central and Southern California have less than 25 percent of average.

Snow depth in the Sierra Nevada Tuesday averaged just 2.6 inches and covered only 37 percent of the region, the weather service said. A year ago, it was almost a foot deep on average, blanketing more than 70 percent of the mountains.

With just five days to go, December has delivered a mini-drought to Santa Rosa with just two wet days and .04 inches of rain.

Dry skies and daytime temperatures in the 60s are expected through at least through Sunday morning, with a 'chance of rain' on New Year's Eve and into Monday, the weather service said.

One out of five computer models predicts 'moderate rain and gusty winds' to kick off 2018, Anderson said.

Less than an inch of rain in December is far below Santa Rosa's 30-year average of 6.19 inches, according to government data from 1981-2010. But to illustrate how elusive average is, rain totals for December in Santa Rosa since 1902 range from zero inches in 1989 to 17.89 inches in 1955. In 1956, the city got just 0.38 inches.

In December 2016, Santa Rosa got just above average at 6.75 inches.

December is also the first of three typically soggy months. January averages 5.93 inches of rain in Santa Rosa, followed by February with 6.02 inches, with the city's annual total averaging 32.2 inches.

March ranks fourth with 4.53 inches, and is known for so-called 'March miracle' storms.

The current outlook for January isn't great, with Accuweather forecasting 4.41 inches in Santa Rosa, compared with 15.61 inches recorded in January, 2017.

But scant rain is just one element of drought, Null said, noting that water supply is another important aspect. The Department of Water Resources reported Tuesday all but one of California's major reservoirs at or above historic averages for this time of year.

Lake Sonoma and Lake Mendocino, the reservoirs that hold Russian River water for 600,000 customers in Sonoma and Marin counties, are both close to their water storage capacity at 82 percent and 99 percent, respectively.

Brad Sherwood, a Sonoma County Water Agency spokesman, said the dry December has been 'somewhat of a miracle' in the wake of the October wildfires that left tons of ash and debris on the ground.

Heavy rains would have swept contaminants into creeks and the river, he said, noting the dry spell has been 'better for the watershed.'

You can reach Staff Writer Guy Kovner at 707-521-5457 or guy.kovner@pressdemocrat.com. On Twitter @guykovner.