“Climate is what we expect, weather is what we get.” Mark Twain
No one likes a rainy day, especially a grape vine. Not equipped with a pair of rubber wellies, vines do not cope well with getting their feet wet. Like all plants, vines need water to survive, but rain fall immediately before harvest can ruin a winemaker’s happy-hour. Rains cause grapes to swell with liquid, somewhat like humans who have downed a few pints on a Friday night. With tipsy homo-sapiens, the excess liquid results in a few trips to the loo. With wine, the bloated grapes produce diluted, watery wine. If rain falls on the vineyard during harvest, then watery residue clinging to the grape skins also thins the wine. Dilution isn’t the only issue when it comes to rain. Swollen grapes are apt to split, creating neon welcome-signs for infectious fungal and bacterial spores. The winemaker then has to struggle with earthy, dirty flavors and naughty bacterial activity that prematurely oxidizes wine, starting it down the path to vinegar.
Dry winds can assist in ventilating the vines, but they blow the sleazy fungal spores around the vineyard. If the breezes come on too strong, then the grapes can be damaged. Photosynthesis also shuts down, halting the grape’s sugar accumulation and flavor development. As with all fruits, sugar accumulation is a key factor in grape ripeness. As sugar levels increase, a grape’s mouth-puckering acid dissipates. If weather conditions prevent grapes from ripening to their full potential, the result is a tart wine with little flavor, rough tannins, inadequate alcohol – and low market prices.
While sunshine is a vine’s favorite party-companion, too much fun in the sun damages grapes. Since Banana Boat hasn’t come up with grape cluster sunscreen yet, they do sunburn. Periodic heat spikes cause grapes to mature too quickly without developing subtle character. Excessive summer heat will shut down photosynthesis (leaves are temperamental little synthesizers), retarding grape development. And extended sun exposure causes the little grapes to dehydrate and their skins to brown and shrivel like raisins, somewhat like the regulars at Bondi Beach.
As you can see, weather conditions greatly dictate wine quality, hence the hype each year when wines from volatile climates, such as Bordeaux are released. Red Bordeaux wines can be roughly divided into two camps: the right bank and the Medoc. The “right bank” includes the two districts St. Emilion and Pomerol, which produce the famed Petrus and Le Pin. The Medoc, or left bank, houses the classic top Bordeaux estates, which includes the Lafite, Latour, Mouton Rothschild and Margaux properties.
The weather does vary considerably between these two banks, but more importantly, their dominant grape variety differs. On the right bank, the variety Merlot takes center stage in the blend and in the Medoc it is Cabernet Sauvignon that leads the party. Merlot ripens earlier than Cabernet Sauvignon, so fall conditions affect these grapes differently. Once in a blue moon, the Gods are aligned and both banks produce a superb vintage. The year 2009, it seems, is one of those vintages.