Sunday, April 17, 2022

A Slow Start to the Hail Season

CoCoRaHS' annual Hail Week has come to a close, but this post wraps it up with some additional climatological information on hail. If you have been following this week's Messages of the Day you have seen how to measure hail, report it, and how to make a hail pad. (Mobile app users should select "View message of the day" after submitting you daily observation). Hail is a fascinating phenomena and there is a lot of information available if you want to learn more about it. The CoCoRaHS Hail page  has some information, and you can find a lot more information at Living With Weather- Hail on the Midwestern Regional Climate Center website.

Compared to the past few years this hail season is getting off to a slow start. The total number of March hail reports (155) is the lowest since 2011.

Hail reports for January through April 2015-2022

The peak of the hail season is May, June, and July as can be seen in this chart. Note the downward trend in the number of hail report the past five years.

Total hail reports for each year 2015-2022

Normally probabilities for significant hail very low at the end of February and only begin to ramp up in mid-March to early April. Here are the climatological probabilities for significant hail from the the NOAA Storm Prediction Center for mid-April, late May, and August. The center of the high probabilities moves north through April and May, reaching a peak in late May. By early August probabilities are diminished and continue to diminish into early fall.

So far CoCoRaHS observers have submitted 491 hail reports on 60 days (through 4/12), about the same as last year's 498 reports. This map is a compilation of hail reports for the year through April 12 from the Storm Prediction Center. Note that this map is for reports of hail one inch in diameter or larger.

CoCoRaHS has one of the most comprehensive collections of detailed data on hail. While measuring and reporting hail may seem to be secondary to rain and snow, our hail observations provide valuable information not only to the National Weather Service but to others such as the insurance industry. A 2019 article in the Washington Post noted that Texas has experienced 36 $100 million disasters from severe thunderstorms in the past 25 years. Twenty-nine of these $100 million disasters were from hail!

Measuring hail is a core mission of CoCoRaHS, and the separate hail reports on the CoCoRaHS web site allow you to submit your hail information. There are a few things you need to know before measuring hail, and you can find that information in our "Measuring Hail" training animation. Here is a hail size reference and measuring guide you can download, print, and laminate for use. The rule on the bottom is to scale and fits on a 3x5 card. Make multiple copies and keep one at home, in the car, or at work.

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