Now is the time of year to become anxious about what Mother Nature has in store for this year’s grape harvest. We are going to make a barrel of Stagecoach Vineyards Cabernet Sauvignon at Tin Lizzie Wineworks in Maryland this autumn. So we have been monitoring the growing degree days in Napa to get an idea of the potential for this years harvest. Growing degree days is a calculation. Take the difference between the average high and average low for a day. This week Napa has been averaging highs in the low 80ºs and lows in the low 50ºs. The difference is about 30. For each day this week, 30 growing degree days are added to the year’s total. Fifty degrees is the base temperature since there is little growth that takes place below 50º.
As of August 26th, Napa has had about 1,871 growing degree days. Cabernet Sauvignon does well when it is above 2,500 growing degree days. Different areas of Napa Valley will have different numbers. It is interesting to note that currently, the degree days this year are about two weeks ahead of last year. They are also identical to 2009, a year we made wine with Stagecoach Vineyards Cab. The problem with 2009 was a storm that dumped several inches of rain in the area just prior to the Cabernet Sauvignon harvest. Although the growers waited a week for the grapes to lose some of the water they absorbed, the grapes still retained a bit of the water. So far this year, precipitation is much lower than last year and lower than average. If the current trend continues and the rains hold off until after harvest, the 2012 Cabernet Sauvignon harvest will be outstanding.
On the current track, harvest of Cab should take place between the first and third weeks of October. Give a week to transport the grapes across country, we could be starting our wine by the middle to end of October. In 2009, we were destemming grapes on the last day of October. There is a lot of guess work right now. If Napa gets a sudden heat wave with daytime temperatures in the 90ºs, then harvest could be a little earlier. If rains come early, that will affect harvest. At this point, fingers are crossed hoping for a banner year for the grape harvest just weeks away.
Cheers,
Terry
When you look at the temperature charts, the numbers are dramatic. Most wine regions use “degree days,” a heat index that is a measure of accumulated degrees above 50 degrees during the summer season. A typical reading this late in the season for Oakville, the heart of Napa Valley, is about 2,700. This year, until the recent heat wave, it was at 2,300. In Paso Robles, typical is about 3,000; this year, it’s 2,200. Both areas are two to four weeks behind what’s considered normal.