Bay Area heat puts pressure on the wine grape harvest

NAPA VALLEY, Calif. (KTVU) - Hot weather this week has put a bit of pressure on the wine grape harvest. 

The first vintners started picking in the Napa Valley on Tuesday, and may quickly ramp up, as heat hurries the ripening process. 

"Harvest is always exciting, it's a little bit like New Year's Day," said winemaker Tami Lotz at Mumm Napa, which brought in more than 100 tons of pinot noir on Thursday. 

Mumm, a leading producer of sparkling wines, always starts early, before sugar content rises too high. 
Lotz has been watching- and tasting- for a month, waiting for the right acidic balance.   

"You want that bright flavor, and then you make the decision and it's 'Go Time'," said Lotz. 

At Mumm's production facility on Silverado Trail, forklifts are dumping box after box of freshly-picked grapes into the processor. 

By the end of the season, Mumm will process 4,000 tons of grapes.   

Staffing in the plant, lab, and cellar has tripled to more than 30 people. 

Shifts run from 7 a.m.until well past midnight, and next Monday, Mumm will move to a 24-hour operation, thanks in part to the heat. 

"The heat will accelerate the ripening of the grapes, so that means we'll just have to bring it in a little sooner than we thought," explained Lotz. 

Farming is always subject to the whims of weather. 

In late May, unseasonably late rain and wind were a worry, and may have shortened the growing season, even shrunk the yield slightly.  

"But since then, we've had a nice warm summer that let everything even out and some beautiful flavors develop," said Lotz, "and last year was bountiful, a huge crop, so this year we're back to a more normal, average yield but the flavors are great."  

Fruit is picked in the early morning- better for workers and grapes. 

Mumm's first day brought in 18 tons, then 80 tons on day two.

Thursday's haul was 144 tons. 

Next week, when running at capacity, 200 tons will be processed each day, equivalent to about 700 picking boxes. 

Grapes go into a gigantic presser where an inflated balloon crushes them against the side. 

The juice flows into huge stainless steel tanks for the first round of fermentation.

A second round happens in the bottle, where yeast produces carbon dioxide, which makes the bubbles.  
"What you're left with is clean and clear wine in this same bottle," noted Lotz, "and so the bottle you buy is the bottle it fermented in."    
Lotz was an intern at Mumm, before honing her skills in Germany and Chile, then returning to Mumm 16 years ago.

She considers wine-making the perfect blend of art and science, and sparkling wines have always been her favorite.   

"It was the first type of wine I ever tasted and I fell in love with it." 

Knowing that soon, the crush will intensify across Napa, Sonoma, and Mendocino Counties, just adds to the anticipation. 

 "That's the great thing about harvest you get filled with adrenaline, because it's exciting."