In less than two weeks, another grape harvest will be under way in France. Conditions in 1983 have been favorable, except for a July hailstorm that ravaged several small, prestigious vineyards in northern parts of the Burgundy region. Grape crops in all areas are expected to be larger than normal and "barring a catastrophe, one can see a very attractive harvest," says champagne producer Christian Pol-Roger.

The temptation, however, to predict another great vintage this fall should be resisted as just wishful excess in the wake of persistent euphoria over the 1982 harvest. With the skidding French franc and a worldwide wine glut, another grande anne'e would be good news indeed for American consumers, but, alas, it does not appear likely.

For almost a year now, serious grape talk and nearly all the wine literature has focused religiously on a single subject: the 1982 Bordeaux vintage. It was widely heralded as the finest claret since (pick one: 1947, 1953, or 1961) and American consumers have responded to transatlantic reports from barrel-tasting experts in an unprecedented stampede to purchase thousands of cases of 1982 "futures" from overwhelmed (but it is hoped, not overextended) wine retailers. Some of the 1982 claret, most of which will not be bottled for another year and will not arrive in America until the spring of 1985, was reportedly "bought" in Texas and New York before it even was sold in France this spring.

There are similarities between the now-ripening 1983 crop and the greatly ballyhooed 1982 vintage. There were no damaging late-spring frosts and the flowering went well again in June. In both years, July was very hot and August was relatively cool with scattered showers throughout the region. The size of the grape crop is again above average.

Similarities, yes. But a repeat of last year's successes is unlikely this harvest for two reasons. First, 1982 was a year of early ripening, primarily because of an early June flowering. This year's crop flowered, on the average, two weeks later than last year. Most of the great vintages in recent years (1959, 1961, 1966, 1982) occurred in years of early flowering where the grapes benefited from the long daylight hours of June and July.

But the real story of 1982 was a tale of September. A burst of hot weather boosted sugar levels just prior to the harvest and thus between the 6th and the 20th transformed a merely good vintage into an exceptional one.

"Bordeaux has seldom seen such a long time of hot days and hot nights," says Bruno Prats, proprietor of Cha teau Cos d'Estournel in St. Estephe. "The hot nights were instrumental in lowering the acidity and making the wines more supple," he adds. History indicates that weather conditions this month are unlikely to be that favorable again.

Pierre Ribereau-Gayon, director of Bordeaux's Institute of Oenology, terms the 1982 harvest "spectacular," noting that the overripe grapes had unusual concentration. The fermenting juice of the newly crushed red grapes had high levels of alcohol, resembling a California harvest. Some vats of merlot registered at 13.5 percent alcohol. Twelve percent is normal. Indeed, the hot weather continued through the first weeks of the harvest, reportedly presenting temperature control problems during early fermentation for a few producers.

Thus, not only was the 1982 vintage blessed with an unusually hot and sunny September but the early harvest meant that the burst of great weather came at the ideal time--at the end of the grape maturation process. The following chart (prepared by Ribereau-Gayon) demonstrates the correlation between a warm September and three recent extraordinary harvests.

Favorable conditions are also necessary to achieve proper levels of tannins, chemical substances that give depth and aging potential to a wine. Tannin levels last year were the highest in recent times.

But, if the quality of the 1983 crop is unlikely to reach such Olympian heights, it is also unlikely to be a disaster. Progress in disease control in the vineyards and modern fermentation techniques in the winery have effectively precluded the likelihood of dismal vintages such as 1963, 1965 and 1968.

"We are able to pick later these days and thus get riper grapes, even in years with a lot of rain during the harvest," says Prats, who adds that the problem of mildew has been alleviated by careful spraying. "In the old days," he explains, "the cellarmaster would simply look at the grapes and taste the berries. Sophisticated analysis simply did not exist." Prats adds, "Now, twice a week we compare sugar levels and overall acidity in modern laboratory facilities." He notes that many cha teaux are aided in difficult years by outside enologists, such as the peripatetic Emile Peynaud, known in the industry as the king of Bordeaux.

"When there is not enough sun, we can extract more tannin and ferment at higher temperatures," Prats notes. "No longer should we have to crush grapes that are in bad condition," he says. "There will be no more of the really bad vintages." So if this year's harvest is beset by drenching rains, chances are that the entire crop will not be lost to rot. By extending the growing season through the application of modern science--much of it developed in California--growers in Bordeaux may at least be able to salvage wines that will be light, lacking complexity because of a deficiency in tannin, but clearly drinkable. Prats at Cha teau Cos d'Estournel and other producers in Bordeaux who were very selective in choosing only their best grapes for their 1980 wines have presented consumers with light, presently drinkable wines from that vintage at less than $10 (Cha teau Branaire-Ducru, Cha teau Pichon Lalande, Cha teau Prieure'-Lichine and Cha teau Figeac). Only when the sun refuses to appear in October does a poor, 1974-type vintage result.

Even in sun-drenched California, every year is not a "vintage" year. And what a problem consumers would have if every year was.

"Wines from the best producers in 'lesser' vintages are often better values than wines from the 'great' vintages," states Prats. In addition, wines from the "lesser" vintages usually are less intense and contain less tannin and thus can be consumed earlier. Conversely, he believes that in vintages like 1982, the consumer can score great bargains with many "lesser" classified growths, such as Cha teau Canon, Cha teau Calon Segur, Cha teau Ch. Grand-Puy Lacoste, Cha teau Prieure'-Lichine, and even unclassified cha teaux such as Cha teau Potensac.

Prats has escalated the widely-publicized debate with California producer Bill Jekel over whether "terroir" (soil and climate) or enology (winemaking) is the more important factor in producing great wines (each clearly has a vested interest in his point of view). The urbane, articulate Prats rejects the notion that Bordeaux producers, emulating their California competitors, have been producing wine in recent vintages that are less tannic, more supple, and destined for earlier consumption than the slow-maturing wines of the past.

"Tannin is actually thousands of different chemicals that are present in the fermenting juice," says Prats. "The tannins in many old wines are those chemicals that make the wine appear hard for a very long time. We have learned how to extract only the soft tannins." Noting that these "modern methods" actually began at properties such as Cha teau Le'oville-Las-Cases and Cha teau Ducru-Beaucaillou several decades ago, Prats believes that the best of the "new" claret--from successful vintages such as 1978, 1981, and 1982--will age just as well as before.

As the sugar levels rise this month in nearly 250,000 acres of grapes throughout the Bordeaux region, so too do the hopes of the Bordelais for another great "twin vintage," like 1928-1929. While such prospects are intoxicating, the realistic expectations are for simply another good, sound harvest. With the franc near an all-time low against the dollar, American wine consumers could do much worse. Wine Postscripts

* Contrary to my report earlier this summer (July 17, "Finding Respect in the Valley"), Los Vineros Winery in Santa Maria, Calif., has not been sold to nearby Zaca Mesa Winery. Negotiations between the two Santa Barbara County producers broke down in July, according to Edwin Woods, chairman of the board of Los Vineros.

* Chateau LaMission Haut Brion has been sold to its Graves neighbor Chateau Haut Brion (owned by American C. Douglas Dillon), subject to approval of the French government.

* The sale of Chateau LaGrange in St. Julien to Santori International of Japan has received initial clearance by key French government ministries.

* Coca Cola's wine subsidiary, The Wine Spectrum, which already owns three California wineries, is reportedly eyeing Parducci Wine Cellars in Mendocino County.

* The best value in a cork-finished white wine just may be 1982 Aveleda Vinho Verde from Portugal (about $3.50).

* California vintners are nervous about long-range weather forecasts that are predicting a repeat this fall of freakish Pacific Ocean storms that plagued wineries during the harvest last year.