Hail up to 2 inches in diameter and 75 mph winds were reported in central Oklahoma.
A meteorologist at the National Weather Service Storm Prediction Center in Norman described the scene as “some of the most intense lightning storms I’ve ever witnessed.”
Thunderstorms formed abruptly on Monday afternoon ahead of a cold front draped southwest to northeast across the central and southern Plains. A springlike severe weather outbreak of damaging winds, hail and even isolated tornado activity were expected, the National Weather Service’s Storm Prediction Center delineating a level 2 out of 5 “slight risk” of severe storms.
A severe thunderstorm watch was issued shortly before 4 p.m., highlighting the potential for “isolated significant gusts to 80 mph,” as well as “scattered large hail and isolated very large hail events to 2.5 inches in diameter.”
Thunderstorms developed explosively during the evening hours, prompting severe thunderstorm warnings. Some towered to more than 55,000 feet tall. Storms were particularly concentrated in the southern Oklahoma City metro area along Interstate 35, including in Norman and Moore.
At 4:20 p.m. local time, a nearby storm brought lightning near Oklahoma’s campus. The University of Oklahoma Department of Campus Safety tweeted that “lightning is within 8 miles of campus.”
“End outdoor activities at this time and limit your outdoor exposure,” they warned.
Storms nearby produced lightning in the area through 9 p.m., with a brief lull before thunderstorm activity ticked up again shortly after 11 p.m.
“Lightning, flooding rain, just stay home and indoors. It is dangerous to be outside,” tweeted OU Campus Safety at 11:43 p.m.
Additional thunderstorms continued intermittently through the night and into Tuesday morning before finally winding down.
“We had many storms, some quite slow-moving,” wrote Kristin Calhoun, a research scientist with the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, in an email. “These storms all had consistently strong, well-maintained updrafts. The updrafts are what drive the storm electrification, so you’re getting consistent charge replenishment to fuel more lightning.”
Nearly 30,000 strikes
Within just a few hours on Monday night, lightning mapping instruments logged nearly 30,000 lightning strikes within the eight-mile safety radius of the OU campus. Most were intracloud (cloud-to-cloud) strikes, but many were cloud-to-ground strikes. According to the National Severe Storms Laboratory, about 5 to 10 percent of lightning discharges strike the ground.
Assuming that even 1 in 10 lightning strikes was cloud to ground, that still comes to between 7 and 15 cloud to ground lightning strikes per square mile — comparable to what parts of western Oklahoma may see in a given year.
“Oklahoma is no stranger to high numbers of lightning,” Chris Vagasky, a meteorologist at Vaisala, wrote in an email. “Last year, the [National Lightning Detection Network] detected more than 14.7 million total (in-cloud pulse + cloud-to-ground stroke) lightning events across the state. Oklahoma ranked number 2 in the country for both lightning counts and lightning density.”
The secret to summertime lightning
It may seem as if lightning is more prolific in summertime storms vs. the generally more violent storms of spring. That’s the result of the structure of storms, which affects lightning behavior.
“The nature of the lightning can be a bit different,” Calhoun wrote. “The lightning flash rate and size are controlled by the size and strength of the storm updraft.”
Supercells, the most powerful type of thunderstorms, most readily form in the spring. Calhoun said those storms can produce hundreds of flashes per minute, their explosive updrafts causing the vigorous charge separation that results in an electrical discharge.
“But the vast majority of these flashes are small, may not give off much ‘light’ and generally do not produce the kind of thunder that rattles your windows,” she explained.
Summertime storms, on the other hand, may be a little less potent, but storms often form in clusters or lines and are taller.
“The flashes themselves can be a bit bigger, dissipating charge over a wider area,” Calhoun wrote. “Because these are larger flashes that often initiate at lower altitudes when compared to the conceptual model of a springtime supercell storm, they are noticed a bit more by people. The extended tortuosity of these flashes produces a bigger/longer sound from thunder, too.”
Tortuosity describes the extent to which a lightning channel is twisted or contorted.
Some storms, especially in the summertime, can even produce “megaflashes.” Those are especially extensive lightning discharges that can occur with mesoscale convective systems, or sprawling lines or clusters of thunderstorms that can span hundreds of miles.
A 440-mile-long lightning discharge was confirmed over Brazil on Oct. 31, 2018.