Record hailstone

Photo courtesy of Colorado Climate Center and Kylee Miltenberger of Bethune.

A new state record for the largest hailstone ever to fall in Colorado has been certified by state weather experts, and a second record — for the hottest day in the state's history — is just days away from being official.

The 8.5-ounce hailstone fell eight miles north-northwest of Bethune, on Colorado's Eastern Plains, on Aug. 13. Its diameter was measured at 4.83 inches, bigger than a baseball.

The Colorado Climate Center at Colorado State University reported the new record, saying the hailstone was produced by a "supercell" thunderstorm that hit the Eastern Plains in Kit Carson County. A team from the State Climate Extremes Committee, including representatives from the National Weather Service, examined several large hailstones, including the record-setter.

The previous, unofficial record was 4.5 inches in diameter. Hailstones of that size have fallen approximately 20 times since the mid-1900s, the Colorado Climate Center reported.

The record hailstone fell near the home of Kylee Miltenberger of Bethune, whose family discovered several large hailstones after a 3 p.m. storm on Aug. 13. Photos posted to social media, first reported by KKTV of Colorado Springs, indicated the record-breaking stone was even larger than was recorded by the SCEC, since Miltenberger picked up the stones about 30 minutes after they fell after waiting out the dangerous thunderstorm.

The Colorado Climate Center estimated the hailstone's original size at larger than 5 inches in diameter, based on those social media posts.

The hailstone was then sent to a cold lab at the National Center for Atmospheric Research in Boulder for preservation and further study, which included a 3D laser scan.

3D image Bethune hailstone

3D image of the Bethune hailstone that fell on Aug. 13. Image courtesy of the Insurance Institute for Business and Home Safety.

The other potentially record-breaking occurrence in Colorado this summer was the 115 degrees Fahrenheit temperature recorded at John Martin Reservoir in Bent County on July 19 by Ian Livingstone of US Tornadoes, a tornado-tracking service. 

The current record of 114 degrees Farenheit has been reported twice — in Sedgwick, on the state's northeastern border, on July 11, 1954, and in Las Animas, in southeastern Colorado, on July 1, 1933.

At the other end of the thermometer, the state's record low of minus-61 degrees was set on Feb. 1, 1985, in Maybell, in northwestern Colorado.

Assistant State Climatologist Becky Bolinger of the Colorado Climate Center told Colorado Politics it's more complicated to verify the record for the state's hottest day than it is to measure a hailstone.

"If you save the hailstone, anyone can measure that. Measurements are easy," she said.

 "When you're talking about temperature, there are nuances," she said. For example, you could put three thermometers in the same spot to see if they all come up with the same reading. Officials also had to determine whether the sensor works at that high a temperature and what the observer recorded.

There's also a question about siting — the sensor that recorded the 115-degree reading was in a sandy area, even though the preferred place for sensors is usually a big grassy, open field, Bolinger said. Another factor could be the local temperatures in the area, including nearby Lamar, which recorded a high that day of 111 degrees Fahrenheit.

The climatologists decided to check the sensor by putting it in an oven at CSU and cranking the oven up to 115 degrees. It turn out, Bolinger said, that the sensor was accurate.

After checking the sensor and other factors, she said, "we feel more certain about this than previous records."

Once all the questions were answered, the decision to certify the hottest temperature was put to a vote. Those voting included Bolinger, State Climatologist Russ Schumacher, a meteorologist from the National Weather Service in Pueblo, and representatives of the High Plains Regional Climate Center, the National Oceanic and Atmospheric Administration and the National Center for Environmental Information.

Bolinger said they agreed the 115-degree reading was valid.

The record becomes official when NOAA publishes the report, sometime later this week, she added.

The Colorado Climate Center attributes the extremes to the state's "interior continental location, combined with complex topography" that "results in dramatic climate differences from place to place and from year to year."

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