Perhaps the most potent storm of the day blossomed over Coahuila, Mexico, during the midafternoon before drifting east into South Texas, where it dropped hail the size of grapefruits. While the largest official report stood at 4 inches, emerging evidence suggests some of the stones may break new state records.
One stone that landed in Hondo, Tex., about 30 miles west of San Antonio, may vie for a state record.
Matt Kumjian, a professor of atmospheric sciences at Penn State who specializes in the study of giant hail, used photogrammetry — a trigonometry-based approach of estimating the size of objects from photographs — to calculate just how large the stone may have been. His estimate? Between 6.27 and 6.57 inches across.
“The photograph contained a reference object (a U.S. quarter coin, which has a diameter of 24.26 mm)," explained Kumjian in an email. “The camera’s perspective was at an angle, so there is a slight skew in the dimensions of the quarter. As such, I used the two extreme measurements of the quarter as references.”
Six inches is a conservative bound, but would still set a new state record if confirmed. The current record is held by a stone that fell on May 20, 2019, in the Texas Panhandle town of Wellington. Similarly massive hail was measured in Smithville, about an hour southeast of Austin, on March 18, 2018.
Hail up to 5.33 inches in diameter pounded Burkburnett, near the Red River, when a strikingly-sculpted rotating supercell thunderstorm loomed overhead last May.
“This means [Wednesday’s] hailstone counts as ‘gargantuan,’” wrote Kumjian, “and is one of only several well-documented cases of such large hail.”
It’s still shy of the world record eight-inch stone that crashed to earth during a destructive hailstorm that struck Vivian, S.D. on July 23, 2010.
Doppler radar estimated Wednesday’s storms towered to more than 64,000 feet tall, virtually unheard of for even the most powerful supercells. Radar also noted a drop in “differential reflectivity,” a radar product that compares the width of objects to their height. Raindrops are flatter, so values are usually positive. When values drop to near zero, it’s indicative of round or tumbling objects — and usually means big hail.
“We’re trying to get more information from folks,” said Mack Morris, a meteorologist at the National Weather Service in Austin, regarding the hailstone. “We have some reports from the person holding the really large stone. One was a landlord, and it was one of their tenants. We’re trying to find exact location, the time it fell. We had another one, connected through one of the folks in town. There have been so many it’s hard to keep track. We’re still actively investigating it.”
He said the investigation is ongoing now, and it could be several days before any potential records are made official.
“There’s one photo of an elongated stone that looks like it’s almost six inches long,” said Morris.
In the meantime, more severe weather is in the offing in Texas — though cantaloupe-size hail is not expected. A Level 1 out of 5 “marginal risk” of severe weather encapsulates southern reaches of the Lone Star State on Friday and Saturday.