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ONLY ON 3: TVA meteorologists track weather, help guide power generation

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CHATTANOOGA, TN (WRCB) -

Weather is an important part of our lives. It impacts everything from clothing choices to livelihoods, each and every day.

The Channel 3 Storm Alert Team keeps a close watch on the conditions and develops forecasts everyday, but there are many other people working behind the scenes in our community to track the weather and keep people safe.

Weather plays a big role in keeping our lights on and power bills down. Severe storms, ice and snow all impact whether our homes have power, but something we encounter every day plays an even bigger role: temperatures.

TVA keeps meteorologists on staff to help make detailed forecasts each day to help operators know how much power to generate.

“We have to match the electricity supply with the electricity demand, so I’m here to make load forecasts based on temperatures, especially heating in the winter and air conditioning use in the summer,” said Jeff House, TVA short-term load planner.

It’s a tricky process and House has to be precise. Temperature ranges aren’t an option. His goal is to be no more than one or two degrees off.

“[The] first step is temperatures, and then [we] go over to the megawatts, which can also be affected by sky cloud cover, winds, humidity, so it’s a lot of science and a lot of art to it as well,” House said.

A mistake could cost TVA big bucks and find its way to customers’ power bills.

“If Jeff is off by three degrees, that’s the equivalent of 650,000 households of power demand that he has either over forecasted or under forecasted,” said Patrick Walshe, TVA manager of resource operations and analysis. “That’s the kind of pressure Jeff is under every day to get the forecast right for us.”

If adjustments are needed, House lets the operators know as soon as possible so they can adjust.

Predicting what the weather will do is tough in a place like the Tennessee Valley with its mountains, ridges and valleys. The exact weather conditions are often different in one place than another.

Precision gets even trickier when looking at the entire TVA service area, which covers portions of seven states. TVA divides the area into five different micro climates to help.

“Memphis is out by the Mississippi River, they have a different climate. Nashville, central Tennessee and then you’ve got Huntsville and Chattanooga, they’re kind of similar, and then Knoxville is up in the northeast. And so those really cover fairly well what’s going on across the service territory,” Walshe said.

House and Walshe agree the most challenging forecasts come from arctic blasts.

“You’re almost always going to be wrong one way or the other. If the front is late, the quick load ramp won’t be there when you expect it. If the front is early, that’s even worse because we’re short power. In contrast, a summer heat wave builds slowly. So it’s easier to get ahead of it,” House said.

“They’re incredibly hard to time. Especially coming down here to Chattanooga. Sometimes the air gets here quicker over the Plateau, sometimes it does not. So it makes for a very tricky forecast for us,” Walshe said. “So we time it out a certain way, if it’s early then we have to bring more generation on line to meet what we have not forecasted. And if it’s late, we’ve got too much generation on line and so then we have to back some of that down until the actual arctic air gets in here.”

Cooler temperatures also can be problematic when they come on the tail end of a heat wave. Timing is everything – and sometimes it’s just impossible to call.

“Timing is critical. And as I said with arctic fronts, one of the other things that gets us big time is the last day of a heat wave. We know a cold front’s coming through, we know a big squall line is going to come through, and we know we’re going to eat it at some point on the load forecast that day, because we cannot not forecast a high enough load to meet demand. But when the cold front comes through, the load collapses,” Walshe explained. “People’s air conditioning [units] stop working because they don’t need to, and we end up with three or four thousand megawatts off, 10 percent off. And it’s just those days we accept that’s the way the weather is and we can’t model it perfectly, but as long as we keep the lights on we feel like we’re doing our job.”

House said he’s found the amount of power needed in the heat of summer and the dead of winter balances out about the same over time.

Fall brings its own set of challenges with the temperature swings that come from mild days and cooler nights.

“I try to look for days like, similar days in the same time of year,” House said. “So in the middle of October, for instance, because we’re getting some pretty crazy swings, 40s at night and 70s by day, fortunately this temperature range the load is not quite as sensitive as it would be up near 90 or down near 20.”

If adjustments are needed, House lets the operators know as soon as possible so they can adjust.

When conditions are uncertain, House consults with other meteorologists at TVA and outside resources to make sure his forecast is as accurate as possible.

House takes it one day at a time, but also looks ahead with a 10-day outlook that helps TVA consider whether to buy or sell power.

“If we’re short on power and we can buy it cheaper on the market, before looking at our top peaking units, which are combustion turbines, which cost more money to run, then we will go buy that power on the market so that we can save money, keep things more economical, serving the people of the valley, keeping prices down, and keeping the rates down,” Walshe said.

It’s a lot of pressure, but House’s track record is one of the best in the industry and a good forecast brings him satisfaction at the end of the day.

“If I can do my job right and help everyone else do their job right, the lower the costs we have here, the lower the rates we pass through to the rate payers. So I try to think about that every day,” he said.

Rain and snow also have a big impact on our area, as TVA moves water through the dams to generate power and regulate water levels. TVA’s river management is based out of its offices in Knoxville.

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