Early to start, the 2013 North Coast winegrape season is heading toward largely an early finish this month and is sizing up to be above the average for the past several years, in some cases rivaling last year's record crop.

[caption id="attachment_81446" align="alignleft" width="360"] Workers empty tubs of cabernet sauvignon grapes at Trefethen Family Vineyards' Hillspring Vineyard in Napa Valley's Oak Knoll district on Oct. 9.[/caption]

Picking is into the home stretch in Sonoma, Napa and Lake counties, though in a pause in Mendocino County, according to growers. Two back-to-back big harvests are prompting a number of winemakers to consider viticultural plans to recharge grape vitality as vines show signs of deficiencies in nutrients such as potassium.

Based on the number of days this season warm enough to spur vine activity -- called degree-days -- the tally through September at Trefethen Vineyards' main ranch in the Oak Knoll winegrowing region of central Napa Valley has been cumulatively warmer than the pace through October in the past six years, according to Jon Ruel, president of the winery and the board of the Napa Valley Grapegrowers trade group.

That would suggest the season is a month ahead of what's typical, but development of phenolics and other quality aspects of the grapes suggests the season is two weeks ahead, he said. Trefethen started picking chardonnay in early September for the first time in several years and is well into picking cabernet sauvignon, Napa Valley's dominant variety.

"It is a great year but stressful with so many decisions on when grapes are ready to pick and the tank you want to put them in is full," Mr. Ruel said. "It’s certainly a lot more fun when the sun is shining and wines taste great."

Harvest was nearly 90 percent complete in Sonoma County and is trending toward a finish in the third full week of this month, according to Karissa Kruse, president of Sonoma County Winegrowers.

Sonoma Valley grower Steve Sangiacomo, also a board member of Sonoma County Winegrowers, said he is finishing harvest of chardonnay and pinot noir from Los Carneros, Sonoma Valley and the Petaluma Gap area of Sonoma Coast this week. At a projected 4,500 tons crushed, the volume is on par with that of last year, he said.

"It was kind of nerve-wracking to have to dodge two rain events, but we’re very fortunate," Mr. Sangiacamo said. "We got lots of dry winds afterward, and the vines got dry within 24 hours."

An early harvest can be problematic for winegrape flavor development, but 2013 brought a relatively trouble-free season to methode champenoise wine producer Korbel, resulting in "nice even, slow ripening," according to Paul Ahvenainen, director of winemaking.

"The harvest was early because we had a very good growing season in the spring. So, the magical 'hang time' was actually normal," he said.

He said Korbel's cuvee wines are trending toward "a nice crisp acidity, without being aggressive," Mr. Ahvenainen said.

Russian River Valley chardonnay and pinot noir cuvees, in particular, have ample fruit flavors, and "nice depth and intensity," he added.

Quality of the what's going into tanks and barrels in Sonoma Valley's Kenwood Vineyards, part of the Heck Estates portfolio, is "exceptional," said Pat Henderson, senior winemaker.

"The reds in particular have great color and structure and lots of natural acidity," he said. "We won't be able to really see what they taste like until the malolactic fermentation is finished and they have had a couple of months to settle down, but I expect 2013 to be one of the best vintages in a while."

Rodney Strong Wine Estates, which produces about 800,000 cases a year from 1,300 acres of owned and leased vines as well as grape purchases from two-thirds more acreage, is trending toward handling 10 percent to 15 percent more grapes than the five-year average and plans to wrap harvest this week, according to Douglas McIlroy, director of winegrowing.

"It was one of the warmest growing seasons in 30 years -- not in hot days but in degree-days," he said. "1992 is the year I think about having as many degree-days. I haven't heard of bloom having come this early in 30 years -- like early 1980s."

Clay Shannon, vintner of Shannon Ridge Winery in Lake County, anticipates another two weeks of picking, currently progressing through cabernet sauvignon, petite sirah and some zinfandel as leaves turn color on the trees and vines. His vines weathered the two rainstorms and subsequent cold nights, including one with frost, to bring fruit to optimum quality in the first two weeks of this month.

"It’s a a perfect way to finish up harvest -- really ripe fruit, great color," he said.

As growers in Sonoma, Napa and Lake counties scurry to pick remaining fruit, those with vines in Mendocino County are playing a waiting game after a fast start to harvest in early September, according to Zac Robinson, co-owner of Husch Vineyards in Anderson Valley and president of the year-old Mendocino WineGrowers marketing group. After the late-season rains, grapes largely stopped ripening.

"In the late vineyards now, fruit quality is there and the grapes taste good, but sugar is not there and wineries are hesitant to pick," he said.

Now, those vineyards are a week to 10 days behind.

"Every year is funky, and this is by no means a crisis," Mr. Robinson said.