Pahlmeyer vineyards in Napa Valley, autumn 2015 Credit: Pahlmeyer / Instagram

In many areas, inclement weather during flowering resulted in shattered grape clusters, making small quantities inevitable from the very beginning.

Vines fatigued by three years of drought and three consecutive generous vintages (2012-2014) also tended to produce smaller berries than usual. This phenomenon was most conspicuous in Pinot Noir, but Chardonnay was also below average.

On the Sonoma Coast, Jasmine Hirsch reports record low yields of 0.8 tones per hectare, and to the south in Santa Barbara the story was the same. Further inland, Pinot yields were less punishing, and the Napa Valley Cabernet Sauvignon crop, while depleted, did not suffer so badly.

These small crops ripened rapidly, and when harvest came it was, as Cathy Corison puts it, 'fast and furious'.

Pinot Noir and Chardonnay were picked first, beginning in August, followed unusually swiftly by Cabernet Sauvignon.

A series of heat spikes in September saw sugar accumulation accelerate rapidly, in advance of physiological maturity, a problem exacerbated by low yields and drought conditions.

Some Napa Valley vintners opted to pick early, others to wait it out in pursuit of riper tannins and deeper colours. But for everyone, this was a remarkably early harvest.

At this early stage, quality looks very promising. Low yields have resulted in exceptional concentration and intensity.

Consulting winemaker Thomas Brown believes the wines may be able to compete with the extremely successful 2013 vintage.

But there is very little wine. In Santa Barbara, Raj Parr, of Sandhi and Domaine de la Cote, said that quality is very high, but wishes he had a little more, and throughout the state the refrain is the same.

Eric Baugher at Ridge Vineyards said there was exceptional quality and perfect ripeness, but production fell by 33%.

These wines, then, will be scarce, but fascinating to follow over the next decade and beyond.