Cooler weather is expected to move into the region this week, with the possibility for record low temperatures overnight.
According to the National Weather Service in Calera, the forecast low temperature for the Anniston area on Thursday is 58 degrees; the previous low for the date was 61 in 1965. The pleasant conditions are expected to last until Saturday, giving way to more rain.
A number of media outlets, including the Weather Channel, have attributed the cooler weather to a phenomenon known as the polar vortex, but weather experts are wary of using the term polar vortex and claim that the forecasted weather is not an extreme event.
“It’s sort of a made-up term,” said Kevin Laws, a science and operations officer at the National Weather Service’s Birmingham-area office in Calera. “It’s nothing more than a bigger weather system. It’s a little unusual, yes, but not unheard of.”
The polar vortex refers to a large, cyclonic mass of cold air centered high in the Earth’s atmosphere around the polar regions and strongest during the winter months. Occasionally, portions of the vortex will break off from the larger rotation and plunge south into the United States, evidenced by the past winter’s cold wave.
“Every now and then, you’ll get an unusually large southward amplification in the jet stream and circumpolar vortex and that’s what we’re seeing here,” said Keith Blackwell, a professor of meteorology at the University of South Alabama. “That pattern persisted over and over again during the wintertime, which is when the word polar vortex gained notoriety.”
Following the winter months, the vortex rapidly shifts northward.
“As the sun is further northward in the spring and early summer, the vortex shrinks, moves further north and so does the jet stream,” said Blackwell. “It takes the winter storms and strong frontal activity with it.”
Bill Watkins, who works at Crystal Springs Lake in Wellington, noticed a significant decline in the number of swimmers on Wednesday.
“There’s just not as many people out here,” he said.
The area last encountered a similar weather situation only two weeks ago, with cool, dry air arriving in time for Independence Day.
“When a system gets going across the northern U.S., it will pull that colder air down from northern Canada,” said Laws. “We had a similar system come through on July 4 that didn’t get as much attention.”
“It has lobes that extend down over the world,” said John Christy, Alabama’s state climatologist. “This weather is more or less a cool front that has come through, not part of a real long-range pattern. You should always remember that when there’s a cool push somewhere there’s a hot push somewhere else. Right now, that is out west.”
According to Blackwell, Alabamians have nothing to worry about.
“It’s only going to last a very short time,” he said. “I don’t think we can link this particular event to what we will see in the winter.”
Staff Writer Tim Steere: 256-235-3551. On Twitter @tsteere_Star.