New ways of hail research

Thunderstorm season continues across the U.S. east of the Rockies. For the 2024 season, there have been 1,344 tornadoes spawned from severe thunderstorms, compared to an annual average of approximately 1,200. Scientists claim that 2024 was one of the most active tornado seasons in history, especially during the spring. For example, in May, there was at least one twister reported in the U.S. nearly every day.

On Aug. 13, there was a tornado warning in eastern Idaho that lasted for about an hour. The regions that were under the warning were Jefferson, Butte, Bonneville and Bingham counties. Radar data indicated the possibility of tornado development on that afternoon, but there were no reports of one that formed. However, there were reports of hail from the severe storm last week.

Although we do see a number of strong thunderstorms that develop in the spring and summer months in North Idaho, large hail is rare in this part of the country. In July 2006, a severe thunderstorm flooded parts of Spokane and areas to the north of that city but barely missed Coeur d’Alene. To the west, golf ball-sized hail was reported in the Post Falls region. There were many reports of damaged gardens, as flowers were literally “flattened” on the western edges of Kootenai County by the fast-moving storm, which pushed northward into Canada in a matter of a few hours.

Hail will consist of balls or irregular lumps of ice that form in thunderstorm-type clouds called cumulonimbus. It forms when there are strong, upward motions of air and the water in the cloud will freeze as it moves up into the cloud. With updraft wind speeds as high as 110 miles per hour, the hailstone can move up and down in the cloud. As it descends through the cloud, it receives another layer of supercooled water droplets. As it moves up the cloud, the water droplet freezes once again, and the hail stone becomes bigger. The ball of ice falls to the ground when it becomes too heavy in the cloud.

According to Wikipedia, the heaviest hailstone was 2.25 pounds and fell at Gopalganj District in Bangladesh on April 14, 1986. The largest diameter officially measured was 7.9 inches at Vivian, S.D., on July 23, 2010. That particular hailstone had a circumference of 18.622 inches and weighed 1 pound 15 ounces. But, the largest circumference, the distance around the ice, was 18.74 inches, which fell at Aurora, Neb., on June 22, 2003.

In the U.S., most of the thunderstorms will occur in Florida. However, most of the hail that is reported is often found in Nebraska, Colorado and Wyoming. These states will average approximately seven to nine hail days per year. According to NOAA, China, Russia, India and northern Italy will also experience damaging hailstorms.

Hail research and forecasting have been increasing in recent years to better understand and predict these damaging storms. A research paper that was published in the Journal of the Atmospheric Sciences uses the various sizes and shapes of hailstones to help predict their pathways, speed, and impact.

Like snowflakes, no two hailstones are completely alike. Many will often have odd shapes rather than a perfect sphere. Hailstones can be nearly flat or have spikes originating from the center of the stone. According to an article by phys.org, by examining and modeling the different shapes of hail, scientists may ultimately help predict in “real-time” how big a hailstone might be during a major storm and where it will fall.

To help with these new technologies of hail prediction, frozen hailstones have been collected at a University of Queensland library located in eastern Australia. Hundreds of samples were scanned using 3D technology. It’s essentially a “hailstone library,” which is a relatively new science dedicated to forecasting severe weather. 

In terms of our local weather, we finally received some measurable rainfall last week. At Cliff’s station, 0.11 inches fell Friday, taking the August precipitation total to 0.25 inches. Only 0.02 inches fell at Spokane’s International Airport, but over a half inch of rain fell at Kellogg with 0.41 inches in Hayden. There were some isolated areas near Coeur d’Alene that received over a half inch of much-needed rainfall.

We’ll likely have some scattered showers over the next several weeks, but not much moisture is expected across the Inland Northwest through the rest of August. Unless there is an isolated thunderstorm that drops some heavy rainfall in a short period of time, we’ll likely have another month with below-normal rainfall. During an average August, Coeur d’Alene normally received 0.92 inches of rain. Since the astronomical summer season began June 20, only 0.42 inches of rain has been measured in Coeur d’Alene.

The drier-than-normal weather pattern is expected to continue into September. However, with the cooling of sea-surface temperatures, our region will likely “flip” to the cooler and wetter side later in September or October. November is expected to be wetter than normal as well.

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Contact Randy Mann at randy@longrangeweather.com.