Day four of the California trip. By now, the group was certainly performing, and this was to be one of our strongest days in terms of banter and general foolery. Of course, we were utterly professional. But bus banter is so important for a trip like this, and everyone played their part.

First of all, though, a note on the weather. It was shocking. Heavy rain all day, culminating in us all getting rather alarming weather warnings on our phones in the evening. This was new to me: I didn’t know that phones could do this. But where there is a severe risk (here, it was flash flooding), the mobile phone operators are able to send out alerts that make your phone go off in an audible alarm with a message detailing the specific risk.

The day began at Peter Michael Winery (there’s a very interesting profile of Sir Peter here). We were hosted by winemaker Nicolas Morlet, who is from Champagne. He took over winemaking duties here from his brother, Luc Morlet, who still consults. Their family domain is Pierre Morlet & Fils in Avenay-Val-d’Or. But here, in Knights Valley, the Napa Valley and Sonoma, Peter Michael is, in ripeness terms, pretty much the polar opposite of Champagne: the wines are made in a very lush, generous style.

We had a look at the Knights Valley vineyards. This is the home patch, a 630 acre estate on the volcanic ridges of the west face of Mount St Helena, and despite the rain, they looked quite stunning. There are just over 130 acres here, planted with Chardonnay and Bordeaux varieties, in five separate vineyards. Then there are a further 26 acres in the more recently acquired Au Paradis vineyard in Oakville, Napa, and 30 acres of Pinot Noir at Seaview-Fort Ross on the Sonoma Coast.

We tried through quite a few of the wines, with a couple of library releases. I found the Sauvignon Blanc, at 15.5% alcohol, to be far too ripe and unfocused, and felt that while the Chardonnays were impressive, they might have been better picked earlier (they were above 15% alcohol also). But the 2011 Caprice Pinot Noir was delicious: lush and pure, but still with freshness and a very silky texture. And the 2013 Au Paradis, from Oakville, was a concentrated, structured expression of Napa Cabernet (77% Cabernet Sauvignon, 23% Cabernet Franc), which carried its ripeness (14.9% alcohol) very well. These are, with the exception of the Sauvignon, high quality wines, but they cater for those who like their wines on the ripe side.

Next up: Corison. Cathy Corison has been the standard bearer for making a more balanced, ageable style of Napa Valley Cabernet, and she makes just two wines (not counting a small-production Anderson Valley Gewurztraminer) – her Cabernet Sauvignon and the single-vineyard Kronos Cab.

The latter is made from a 45 year old vineyard behind the winery, from paltry yields of 17 hl/ha (1.25 tons/acre) in an average year. The berries are so small, she has to run the crusher at half speed. Cathy harvests around three weeks earlier than the average, but this is beginning to change (others are beginning to harvest earlier too), so it is now getting more difficult to find harvest crews, a problem she’s never had before. We tried the 2006 and 2011 Corison, and both were fabulous wines. The 2011 and 2012 Kronos were also sensational, with a slight extra dimension. It’s no wonder these wines have such a good reputation.

This was followed by lunch with Barry Wiss at Trinchero. They have a centre dedicated to hosting and educating the trade, and 10 000 people visit it each year, which is remarkable. The Trinchero story is an interesting one. Back in the late 1940s Mario and Mary Trinchero left New York City and headed off to the Napa Valley, then a sleepy agricultural area, with their children, Bob, Roger and Vera. They bought an abandoned winery called Sutter Home, and slowly built the business. (Apparently, Bob Trinchero, when asked about why they didn’t rename the winery with their own family name, replied that they couldn’t afford to repaint the sign.) They built a reputation for Zinfandels from Amador County. Then, in 1972, Bob decided to make a Zinfandel rosé. For the first two vintages, this white Zinfandel was dry, but in 1974 a stuck ferment left it with some sweetness. Its reputation spread throughout the country, and Bob started getting lots of orders. The success of this Sutter Home white Zinfandel was unparalleled, and it went on to build the fortunes of the Trincheros.

The white zin at its peak was selling 4 million cases annually; now it sells around 3 million and has plateaued. With lunch we tried a range of wines, and the highlight for me was the Terra D’Ora Deaver Vineyard Zinfandel, from 130 year old vines in Amador County. It’s pretty serious, but isn’t expensive.

We then headed off to Silverado, which was founded by the Millers (Diane Miller was the daughter of Walt Disney) in the late 1970s in the Stag’s Leap district. Their first wine was released in 1983 (the 1981), and since then they have quietly been making excellent, balanced and well priced wines. Tasting through the range I was reminded just how good the Merlot and Cabernets from Silverado are. I particularly liked the 2012 Estate and Solo Cabernet Sauvignons.

Final visit of the day was a dinner visit at Chimney Rock, another Stag’s Leap property, and it was memorable. We had a lovely time with the talented Elizabeth Vianna, who is winemaker and General Manager here.

The winery was established by Hack and Stella Wilson in 1980 (so it’s from the same era as Silverado), and then sold to the Terlatos in the early noughties. Hack didn’t sell to the highest bidder, but chose the Terlatos because he was convinced they’d keep the winery running along the way he wanted.

Chimney Rock is another producer who flies under the radar a bit, and the wines are balanced and delicious. The Elevage Blanc, a blend of Sauvignon Blanc and Gris, is delicious and ages well. The Elevage red also ages well, as a bottle of 2002 showed. The Estate Cabernet Sauvignon 2012 was beautiful, and a magnum of the 1995 had developed in a really nice way. I really liked the 2013 Tomahawk Cabernet and the 2012 Omega Point Cabernet Sauvignon was equally remarkable. It was such a nice evening.