By Jon Erdman, Weather Channel

The first 10 months of 2013 have been the driest such period on record in California, dating to 1895, according to the National Climatic Data Center.

Compare the rainfall so far in 2013 with the average-to-date totals through Nov. 14. Some locations are running over 20-inch precipitation deficits for the year, so far.

As a result, 84 percent of the state is categorized in severe drought, according to the Nov. 12 Drought Monitor analysis. Kern, Santa Barbara, San Luis Obispo, and parts of eight other California counties are considered in extreme drought, one drought category higher in the analysis.

This has taken a toll on the state’s reservoir levels.

California dry years are not unusual. This is the Tahoe Keys pier in November 2009. Photo/LTN file

According to the California Department of Water Resources, several reservoirs are less than 40 percent capacity as of Nov. 13, including Lake Shasta (37 percent), Folsom Lake (27 percent), and Pine Flat Lake (17 percent).

Weather Underground weather historian, Christopher Burt, first raised concern about this worrisome drought in a late October blog post. “Now here it is November 14 and nothing has happened (no significant rain) since my blog,” said Burt in an email to me about this event.

“It’s amazing how we are running 50 percent below the previous calendar record for many spots,” said Charles Bell of the National Weather Service in Monterey in an email to Burt on Nov. 14. “It’s so bad that we thought the data at SFO (San Francisco) was not correct.”

Any Relief?

A critical season looms for the nation’s most populous state.

California has pronounced wet and dry seasons. San Francisco, for example, picks up 85 percent of its average yearly rainfall in a five-month period from November through March. Snowmelt provides up to three-quarters of the West’s freshwater supply. In California, Sierra and to a lesser degree, Colorado River snowmelt, is crucial for reservoir replenishment.

In short, the Golden State needs a wet winter, with a combination of significant rain and mountain snow to replenish groundwater and reservoir levels. You could say California dreaming on such a winter’s day for water resource managers includes a parade of Pacific storms.

Are there any signs of the pattern turning wetter?

This weekend, a pronounced jet-stream disturbance will plunge into the Pacific Northwest and Rockies, but this is not a patten conducive for California rain or Sierra snow.

This week, a Pacific frontal system is expected to finally bring some rain to at least parts of Northern California.

What’s not certain at this time is whether all the significant rainfall will remain pinned to far northwest California, or if it will also spread farther south to thirsty parts of the Sacramento and San Joaquin Valleys, even to parts of the L.A. Basin, not to mention some welcomed snow to the Sierra.

What about the rest of the winter and spring?

Interestingly enough, of the 10 driest October-November periods on record in San Francisco, two years had excessively wet Decembers. Most recently, this occurred in December 1995.

December, January, and February are the three wettest months, on average, in the Bay Area.

That said, it remains to be seen if the Pacific storm track will set up from December through the spring to steer a parade of wet, Pacific storms to the thirsty Golden State.