Squall line, straight-line winds hit city

The storm that hit the Garland County area on Tuesday was a “big squall line,” producing straight-line winds and 2-plus inches of rain, the National Weather Service in Little Rock said Wednesday.

The squall line stretched from north to south across the state, with the most intense parts forming throughout the morning, and into the afternoon and evening across central to southern Arkansas, into Texas and Louisiana, meteorologist Charles Dalton said.

“The strongest parts were in central Arkansas as it moved east across the state,” Dalton said.

“What hit the Hot Springs area was really high winds just off the surface, and by the time you get up to 2,000 to 4,000 feet off the ground, winds were in excess of 70 mph. If you had any kind of storm that was able to push those winds to the ground, you saw tree and wind damage across the state,” he said.

Dalton said that from the photographs he had seen, Hot Springs bore the brunt of the storm, but there was also some damage in Grant County and southeast toward Monticello.

“But probably most of the photos I saw in news outlets and social media yesterday (Tuesday) were from the Hot Springs area,” he said, noting that the 50.4 mph sustained winds recorded at Hot Springs Memorial Field sounded “reasonable.”

“I was so busy, I can’t recall about the duration, but that (speed) doesn’t sound unreasonable, whatsoever. It looks like it was just straight-line winds with the strongest area of winds moving south to north across the lake. When strong winds like that hit lakes there is far less friction — buildings, trees, grass, hills — to slow the wind down, so when that hit the lake that was what helped produce all that damage,” Dalton said.

He also said the 24-hour rainfall total of 2.5 inches reported Wednesday by Entergy Arkansas Inc. didn’t sound “off base.”

“Our observation point at the airport reported 1.8 inches of rain, but when dealing with convections and thunderstorms and stuff, rainfall can vary quite a bit (from location to location).”

He said the Community Collaborative Rain, Hail and Snow Network of volunteer observers, which is used by the NWS for supplemental data, but is not owned or operated by the NWS, reported about 3 inches of rain near the south Lake Hamilton area.

Ted Smethers, Entergy Arkansas Inc.’s senior technical support specialist, said that the utility had to increase its releases from Carpenter and Remmel dams to about 18,000 cubic feet of water per second following the storm.

He said Lake Hamilton peaked at about 395.14 feet above mean sea level and Lake Catherine peaked at 300.23 msl. He said the drawdown level for the lakes, which was reached on Sunday is 394.7 feet msl, plus or minus 6 inches, for Lake Hamilton and 299 feet msl, plus or minus 1 foot, for Lake Catherine.

Smethers said the tributary creeks that empty into the lakes have also peaked and Entergy didn’t anticipate having to increase further releases.

“We hit 18,000 cfs, which wasn’t too bad, but I think probably the hardest thing was for the city’s water intake area where turbid water backs up and Blakely Mountain Dam has to release fresh water (out of Lake Ouachita) to push that out,” he said.

The water intake is located in the upper end of Lake Hamilton, just downstream from Blakely Mountain Dam.

Smethers said Blakely Dam goes into restriction when Entergy’s flow releases reach 13,000 cfs, and fresh water could not be released until around 8 a.m. Wednesday.

Interim City Manager Bill Burrough said the Ouachita Water Treatment Plant, the main production facility for the city, did reduce production due to the turbid water, but there is less demand this time of year and the reduction did not pose any problems.

Smethers said Entergy’s rain gauges on the Big Mazarn Creek showed 2.37 inches of rain and Little Mazarn Creek recorded 2.4 inches, while gauges at Carpenter Dam showed 2.05 inches and Remmel picked up 2.5 inches.

“The rainfall wasn’t the same over the whole watershed and some spots got more than others,” he said.

At its peak, Big Mazarn Creek rose from a normal pool level of 0.83 feet msl to 5.47 feet msl at the Sunshine Road bridge and Little Mazarn Creek swelled from a normal 1.3 feet msl to 11.72 feet at the bridge on South Moore Road.

Max Sestilli, the stormwater manager for Hot Springs, said the city’s emergency warning sirens were not sounded ahead of the storm because the city did not get a NWS alert for any severe weather.

“Should we have? Probably, but we didn’t,” he said.

“That could have been more of a microburst type thing like we’ve seen before, but as far as the sirens, they are used in much more extreme situations that we get advance notices on. If we had expected severe flooding, we’d have been in the emergency operations center ready to push the button at any moment. We were monitoring the weather and stream heights, but when the rain comes hard, the creeks rise, and then go down when the rain slacks up. There was never any threat of flooding,” he said.