Warmer and wetter winter as La Niña bullies jet stream north

Warmer and wetter winter as La Niña bullies jet stream north

February 2nd, 2012 by Pam Sohn in News

UTC sophomore Sydney Lamb walks past daffodils Wednesday on Vine Street.

Photo by Angela Lewis /Times Free Press.

POLL: Do you think recent warm weather is due to climate change?

Normally, January provides the days to talk about our fingers feeling single-tingle digits, and today is when the groundhog is supposed to foretell whether spring will be here sooner or later.

Well, this year, the little piggy is just behind.

Ask the daffodils. And your fingers.

Weather experts chalk up last month's "Juneuary"-like weather in the Chattanooga area to a stubborn jet stream that's being bullied by the devil of weather extremes - La Niña.

And they say not to expect a change for at least the next two weeks. Maybe not even the next month.

"Warmer and wetter than normal" is what the extended forecast calls for, said Mary Black, meteorologist with the National Weather Service in Morristown, Tenn. "For the most part, the colder air is staying above the jet stream."

La Niña and her brother El Niño are the extreme phases of naturally occurring climate cycles in the tropical Pacific Ocean, according to the National Oceanic and Atmospheric Administration.

The impacts of those extremes are felt all over the world, not just in Chattanooga.

"Alaska is having record cold, and Europe is in the deep freeze, but much of the U.S. is warmer than normal," said Paul Barys, meteorologist for News Channel 3.

Barys said La Niña has sent the jet stream up to ride unusually far north over the continent, leaving much of the country to bask in warmer-than-norm temperatures.

He illustrates the weather pattern's effect by comparing the air current called the jet stream to a shallow creek. Think of the La Niña-strengthened high and low pressure systems as big rocks holding the jet stream away from its normal dip toward the South, he said.

Mike Leary, a meteorologist with the National Weather Service in Peachtree City, Ga., said the pattern also has "made us more open to the Gulf" and its moisture.

"It's been bringing the warm Gulf air up, and also more rainfall, and that's been very good for us. We've been trying to get the [North Georgia] reservoirs up because we've been in a drought," Leary said. "Even Lake Lanier has almost gotten up to normal level."

Along the Tennessee River, however, the struggle has been on the other extreme.

The Tennessee Valley Authority this week had to release water at maximum levels to prevent flooding in tributary lakes and streams.

The result had positive and negative impacts. Lots of electricity was produced from the ultimate renewable resource, water used over and over to turn turbines at nine dams along the river's 562 miles.

But the utility and the Army Corps of Engineers also had to halt barge traffic because the river was flowing too deep and too fast around Chattanooga.

Nikki Berger, lead engineer in TVA's river forecast center, said TVA had released enough water by Wednesday to reopen the river to traffic and be prepared for the next downpours.

"We've seen this [warmer and wetter La Niña] trend really from September through now," Berger said. "For our reservoir system that just means we have to stay prepared. We monitor data realtime, and we prepare new forecasts every six to 12 hours. ... We're subject to Mother Nature."

Confused daffodils?

Looking at Chattanooga's January temperature data from the National Weather Service in Morristown, it's little wonder the daffodils have been fooled.

The month's "normal" daily average temperature is around 40.5 degrees, but there was little normal about this January, with only two days striking that balance.

Instead, eight of January's 31 days were cooler than normal, and 21 days were warmer than the norm - a dozen with departures of more than 10 degrees.

As for February, Barys is less trustful of the forecast, but he believes the warmer, wetter weather for sure will stick around for two more weeks.

Perhaps "Floweruary" will mean more blooms.

But forecasters are pragmatic: "The trend is your friend," Barys says.

Using that advice, don't break out the hammock yet.

Remember that February always leads to March, Chattanooga's month of weather madness.

So take a breath, grab the umbrella, and step out to smell the daffodils.

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