Where there's smoke ... there's cooling

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Contrary to popular notion, not all of the thick smoke that obscured the Walla Walla Valley's sky for the better part of last week was attributable to the numerous wildfires burning in Washington and Oregon. A rigorous laboratory analysis of that smoke revealed that 47 percent of it came from Mitt Romney's self-combusting presidential campaign.

But no matter what its origin, the net effect on our Valley weather was the same.

With severely reduced sunshine, afternoon maximum temperatures fell by 10 to 15 degrees off their previous highs, while areas less affected by the smoke maintained significantly above normal temperatures associated with the strong ridge of high pressure responsible for keeping the smoke trapped in the lower layers of the atmosphere.

At times, the smoke was so dense here that visibility was reduced to as little as three miles, and the sun hung shrouded in the gray-brown sky like a Day-Glo orange disk.

In the vineyard, growers lamented the loss of sun and heat as harvest gets under way. Some wondered if the smoke and ash might settling on grapes might have some lingering effect on the flavor of juice and wine.

Such at thing can occur. It happened before when grapes were tainted by smoke from fires in Australia, British Columbia and, most recently, California during a spate of fires touched off by a June 2008 lightning storm.

Many of the the California blazes occurred in close proximity to some of the state's best North Coast vineyards, and the choking smoke that filled the air for days was unfortunately expressed in some of the wines produced that year as having "burnt," "salami," "ash-tray" and "smoked fish' odors, rendering many of them unacceptable as commercial products.

According to ETS Laboratories, the indicators of such a taint are the compounds guaiacol and 4-methylguaiacol. Lab testing is done because the taint itself is difficult to detect in the nose or mouth when tasting affected fruit. Berry sampling -- at 200 to 400 berries per sample -- is the preferred method of testing for the two smoke-taint markers, and their levels can help determine the intensity of the affliction in the fruit or suspect wine.

Fortunately for the Valley, a meandering upper level "cut-off" low pressure brought some measure of relief to the region over the weekend. These pesky systems are notoriously difficult to predict as they are cut off from the upper air flow that guides most of our weather in a generally west to east direction. Without this guidance, they tend to wander like an unsupervised child in a toy store: dawdling, speeding up, backtracking and making random changes in direction with no provocation or warning.

As such, they are one of the weather forecaster's biggest headaches and singularly responsible for the greatest aggregate loss of hair from those engaged in such work. (Your follicularly-challenged weatherperson serves as a "shining" example of this phenomenon). What it did do was stir up the air both in the horizontal and vertical planes and improve the poor air quality a bit. The few drops of rain that fell Sunday helped in that regard as well.

Over the next several days, a couple of weak waves of low pressure will pass through our area with very little or no local precipitation. The first should come through late Tuesday into Wednesday, followed by a ridge of high pressure Wednesday and Thursday that will bring subsiding air for a drier and warmer period.

The second wave comes through on Friday, after which the forecasting models begin to bicker like a couple of 'America's Next Top Model' contestants. The Global Forecast System model shoves the jet stream north well into southern Canada, while the European Center for Medium-Range Weather Forecasts model shows the jet stream will maintain its position over the Pacific Northwest.

The GFS indicates a large area of high pressure just off the Oregon coast for some strong warming next weekend, while the ECMWF is much less bullish with the warming trend.

Both scenarios show a mostly dry regime, with the next chance of rain in Walla Walla pegged on or about Oct. 4 -- or just long enough for a certain college grape grower to harvest his sauvignon blanc and semillon before they get wet -- and possibly moldy.

A lifelong fan of both the weather and the Baltimore Orioles, Jeff Popick is an instructor at the Enology and Viticulture Center at Walla Walla Community College and manages the school's teaching vineyard. Send your questions and comments to him at jeffrey.popick@wwcc.edu.

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