Hailstone Measurement and Record Verification: How Is It Done?

Did you know that if it wasn’t for the public’s assistance, hailstone records would be far and few between? That’s right… many of the U.S. state hail size records would not have been possible without someone reporting what could potentially be a record large hailstone. So, what is the rule of thumb for hailstone measurement and who must verify its weight and size? Here’s the inside scoop!

The National Weather Service and Insurance Institute for Business and Home Safety both play a crucial role in verifying the data brought forward by the public. If you do spot a rather unusually large hailstone, wait until the storm has exited your area to safely pick it up, but use latest, leather, rubber, wool or cotton gloves instead of bare hands to avoid melting. The best way to measure it is with a digital caliper, but if you don’t have one, just use a simple ruler and estimate to the nearest one-eighth of an inch. Measure between the two widest points, this includes from the tip of any spike to the opposite point on the hailstone. 

A kitchen scale works best to measure the hailstone’s weight. The scale should be on a level surface, zeroed out and make sure nothing else is on the scale beforehand. When photographing the hailstone, place a reference object such as a ruler, coin, golf ball or baseball next to it to give an idea of how large it is. If you must place the hailstone on a surface, remember that metallic objects will melt the hailstone faster, so place it on a wood or plastic surface instead. 

If you don’t have the means to measure the hailstone immediately, place it in a sealable plastic bag such as a sandwich bag and squeeze out the excess air to keep it from freezing to another hailstone (if you have more than one) and immediately place in the freezer. However, you will need to measure it within 72 hours to get an accurate account of its size before it starts to vaporize. 

The best way to communicate the information about your hailstone (size and weight) is through social media or by calling or emailing the local weather service office. Include your specific location and if you don’t want to give away your house address (if you spotted the large hailstone on your property), then use latitude and longitude coordinates. You can also use your distance to a nearby landmark such as a park or shopping center. If you need to file an insurance claim for damage produced from the hail, turn on your cell phone location service so that your photos will have the appropriate time and location data. 

On a rare occasion, you could come across a hailstone that is large enough to potentially exceed record-breaking size. Follow the steps listed above to handle the hailstone and measure its diameter and weight. However, see if you can measure its smallest and intermediate diameter as well. Then, contact your local National Weather Service Office or local broadcast meteorologist with the details using social media, email or phone. 

The Insurance Institute for Business and Home Safety has a quick response team that can deploy to a location where record-setting hail potentially occurred. The team is equipped with a 3D laser scanning device to capture precise digital models of the hailstone to use for future studies. The IBHS can be contacted at ibhshailstudy@ibhs.org. 

Finally, the Insurance Institute for Business and Home Safety is responsible for contacting the local weather service office to confirm the hailstone's weight and size for record purposes. Once the information is received, the weather service can then confirm if the hailstone satisifies the criteria for a state record.
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Story Image: A hailstone is seen next to reference objects to determine size. (Courtesy of NWS Wichita, Kan.)