How dramatic is the blossoming of California as a producer of quality wine? Consider the transformation of Sonoma County.

Chateau St. Jean, located near Kenwood south of here, may be - in terms of medals won in recent tastings - the most prestigious single winery in America. Its first wines were made only five years ago.

Sonoma Vineyards, a beautiful modern production center, is aiming to make a million cases of wine a year, all varietal and all vintage dated.

The Jordan Winery will make only one wine, cabernet sauvignon. It intends to hold vintages for aging for five years, something even the Rothschilds of Bordeaux can't afford to do.

These are snapshots of a trio of Sonoma County's 65 wineries today. Here is an account of the Sonoma that was from "The California Wine Book" by Bob Thompson and Hugh Johnson:

". . . Sonoma wines have languished long and deep in the shadow of those from the Napa Valley, one row of hills to the east.

"From the end of Prohibition in 1933 until the end of the 1960s, most of the growers and winemakers in the county were content to dawdle along making red, white and pink wine to sell in bulk to prestigious names in Napa or Santa Clara, or ones with money in the San Joaquin Valley. For all practical purposes there were no vintage wines from Sonoma between 1935 and 1967 . . . After Buena Vista, Italian Swiss Colony, Korbel and Sebastiani there were almost no labels."

Now neither the wine-conscious tourist driving through northern California nor the quality-conscious consumer browsing in a retail store should ignore the appellations "Sonoma" or "Alexander Valley" on a label.

Sonoma's growth as a wine center (vineyard acreage has nearly tripled since 1960) was overdue. More than a century ago, European varietals were planted on the site of the Buena Vista winery. In the 1950s tiny Hanzell was the first to import French oak barrels. The pinot noirs and chardonnays made there set new standards. Then, as now, the land was remarkably well suited to growing grapes.The climate varies from cool to warm. But even where it is warm, fog from the Pacific Ocean (only 20 miles over the coastal range from some vineyards) exerts a cooling influence. Varied landscape provides vineyard planners with any number of possible exposures to the sun. The makeup of the soil varies, too.

There are two distinct wine-producing areas of the county. These are, in the south, the Valley of the Moon (home of Sebastiani. Buena Vista, Chateau St. Jean, Kenwood and Z.D. among others), and in the north, Russian River and Alexander Valley vineyards where one finds Korbel, Simi, Sonoma, Souverain, Geyser Peak, Dry Creek, Foppiano, Pedroncelli, Joseph Swann and others.

To explain Sonoma's new status, wine experts point to the extensive plantings during this decade of chardonnay, riesling and cabernet - the most esteemed grapes - as well as modern (or modernized) wineries and the challenge to outdo neighboring winemakers. There is a lively Sonoma County Harvest Festival at the end of September each year where local wineries vie with one another in a widely respected competition.

Here are thumbnail sketches of six Sonoma wineries visited recently along with reports on some of the wines they offered for tasting. All the wineries, if not all the wines, are represented in Washington with the exception of Jordan. The first release from that winery is not scheduled until the summer of 1960.

SIMI Winemaker Mary Ann Graf. who reads M.F.K. Fisher's classic books on food and cooking to ease the pressures of the harvest, termed the 1978 vintage "difficult." As elsewhere, most varieties ripened at the same time, causing confusion in crushing the grapes and storing the new wine. A total of eight wines will be made.

Simi is considered by many as a "boutique," a term applied to the limited production, "custom" wineries. In fact Simi produces nearly 100,000 cases annually and, although once a family winery, it is now owned by the New York City wholesale firm of Schieffelin. According to Graf. if the term is valid, it's due to "an attitude, a quality standard." The owners, she said, "are sensitive that this is a very people winery, not a factory. They may change the product mix (now an unfashionable 30 percent white to 70 percent red and rose) toward 50-50, but not until we locate the right vineyards and get new oak barrels."

The winery itself - an ivy-covered, stone relic from the last century with wooden floors - is picturesque but not very practical. Seven open-topped wood fermentation vats are still in use, though they will be phased out in time. Graf does have such modern conveniences 25 a centrifuge and she strives to make wines that will be recognized for their subtle complexity and elegance.

She is particularly proud of a "special vintage" 1974 zinfandel, and the rich, botrytis-flavor gewurztraminer ($5 to $6) and chardonnay ($6 to $7) of 1976.

SONOMA VINEYARDS: One of the great gambles of recent wine history appears to be paying off here.

Rodney D. Strong, a former dancer and dance director, built a mail-order wine business into a beautiful, three-million gallon capacity winery and 5,000 acres of land. Recession hit. Much of the land was sold and the winery was threatened. Renfield, an importer and wholesaler, stepped in with additional capital. The vineyards Strong had planted with chardonnay, cabernet, pinot noir and rieslings, matured and began providing resoures for award-winning wines.

This past year, Strong reported, sales hit 500,000 cases.

His aim is to make "really good wines at reasonable prices." Several gold medals on display from recent Sonoma and Los Angeles County fairs are evidence that he is doing it. In time be would like to use only estate grapes for the "big four" wines.

He has taken a cautious approach to vineyard designation, but now produces three of them - River West chardonnay. Alexander's Crown cabernet and Le-Baron riesling. All have been medal winners. "These are not just going in special cellars," he said. "I made 10,000 cases of River West and 5,000 cases of Alexander's Crown. The general public can buy them. They can go on wine lists and the restaurateur will be able to get a reorder." These wines have been priced at less than $7 a bottle, though their artistic success has pushed retail prices higher. The regular chardonnay is on sale in Washington for about $5.

In addition to these wines, Sonoma Vineyard's 1977 Johannisburg riesling and 1974 pinot noir should be real crowd pleasers.

JORDAN: A beautiful facility overlooking the Alexander Valley, this new winery has caused a lot of comment because of its opulence and the undisguised ambition of its owner, oilman Tom Jordan, to produce a magnificent American cabernet. If the wines that emerge echo the exceptional attention to detail and good taste evidenced in the physical plant, has goal may well be reached. Michael Rowan directs the winery and the vineyards with advice from the legendary Andre Tchelistcheff, who also consults at Simi.

Rowan said the 1978 wines were made from 100 percent Jordan grapes. Last year's contained 15 percent purchased grapes. For the first, 1976, their vines had not matured enough to provide more than 35 percent of the grapes. Fermentation is done in stainless steel tanks of capacities ranging from 3,000 to 2,000 gallon. For aging, the winery has American and French oak, including some used barrels purchased from Chateau Lafite-Rothschild. There is warehouse storage for 100,000 cases of wine. "Most consumers are denied access to older wines," Rowan said. "We want them to have the choice of several different vintages of our wine - all aged enough to be drinkable - at the same time."

To some such a program is folly. Tom Jordan and Mike Rowan concede they are romantics, but claim their program will make commercial sense. The retail price will be within the range of Brodeaux clarets, but well below first growths.

CHATEAU ST. JEAN: Richard Arrowood, the winemaker here, will make 40 to 45 separate wines from the 1978 vintage. Last year he made 39. Such handcrafting is unprecedented. St. Jean (pronounced as is the American names) has a total capactity of only 35,000 to 40,000 cases. Arrowood has been in the forefront of those experimenting with sugar rich, botrytis-infected grapes (also known as the Nobel Rot). He produced a 1977 Johannisberg riesling "individual dried bunch selected late harvest" with a very high residual sugar of 28.2 percent, similar to the sugar content of a French Sauternes or a German wine in one of the auslese categories. He also has won awards with chardonnays (he has made as many as seven from different vineyards).

It will be another year or more before the winery is completed and St. Jean's own 250 acres of vineyards - some of them on dramatically steep hillsides behind the winery - are in full production. "We're artists doing our own thing," said a St. Jean executive.

St. Jean wines are expensive, $8 or more for chardonnays and up to $40 for the dessert wines, which provides a burden of maintaining consistently high quality. While St. Jean has gained its reputation for its whites, it aims to make a few reds "way above the ordinary" and has a sparking wine on the market as well.

Its 1976 Wildwood vineyard chardonnay and cabernet are impressive, as are a 1976 Sonoma County merlot and separate late harvest rieslings from the vineyards of Victor Matheu, Belle Terre and Robert Young.

KENWOOD: Located only a few hundred yards from St. Jean, this old winery has been renamed, retooled and expanded by the Lee family. A pond, a warehouse and a new riesling vineyard are being constructed. Though not as well financed nor as ambitious as its famous neighbor. Kenwood has been heralded for its generic red, zinfandel and other reds. A production level "near 25,000 cases" suits Kenwood fine, said Marty Lee.

Among its recent wines are a full-bodied, pink-tinged 1977 pinot noir blanc, a bargain-priced 1974 burgundy (over 90 percent pinot noir) and a fine 1976 chardonnay from the Sonoma Velley.

SOUVERAIN: This handsome winery contains a public restaurant as well as storage facilities for 2 million gallons of wine. This year the plant was functioning at full capacity, though less than half the wine - about 160,000 cases - will be labeled Souverain. The rest is being made for secondary labels or for companies without winery facilities of their own.

One of the great attractions here is the winemaker, Bill Bonetti. He is a genial, unfailingly polite and charmingly enthustastic man who previously made wine for Gallo and Charles Krug. Somehow he has imparted to the long list of attractively priced Souverain wines a sense of continuity and shared style. The whites particularly are light, fresh tasting and pleasant on the palate without off-odors or strong acidity.

After considerable financial problems, the winery is controlled by a group of growers. Bonetti is cautious in his use of oak and of the centrifuge, which, he feels, "can strip a wine" of its character if care isn't taken. His 1978 rose of pinot noir holds considerable promise, as does the pinot noir itself. Souverain's rose of pinot noir now on the market sells for about $3. The pinot noir is in the $4 to $4.50 range. Of other wines now in release, his 1977 chablis (a dry version for a little over $2), fume blanc and columbard blanc ($3) were particularly impressive.

Here is a salad dressing recipe from the California wine country, created by Yvonne Boullnay for guests at Sonoma Vineyards. SONOMA SALAD DRESSING

(Makes 2 cups) 1 large, very ripe avocade 1 cup homemade mayonnaise 1/2 cup heavy cream or yogurt 4 tablespoons lemon juice 1/2 teaspoon salt and freshly ground pepper to taste 1 tablespoon wine vinegar 1 tablespoon chopped fresh dill, or 1 teaspoon dill weed 1/2 teaspoon mixed herbs such as thyme, marjoram and parsley

Mash the avocado in a bowl. Add the mayonnaise, cream and seasonings and stir together well.

Use to dress shrimp or crabmeat and serve on leaf lettuce garnished with tomato slices.