Severe weather warning now requires bigger hail

The change allows for a uniform standard nationwide.


The minimum-size hail criterion for severe thunderstorms increased nationwide this month from the size of a penny to the size of a quarter.

Courtesy National Weather Service
Published: Friday, January 15, 2010 at 6:01 a.m.
Last Modified: Friday, January 15, 2010 at 12:16 a.m.

Effective this month, it will take quarter-size hail for the National Weather Service to issue a severe thunderstorm warning or severe weather statement. Previously all it took was penny-size hail.

John T. Ferree of the National Weather Service's Warning Decision Training Branch said the change was made so that there would be a uniform standard nationwide.

A few years ago, the larger-size hail criterion began to be used by weather service offices providing forecasts for Kansas. During the spring and summer of 2009, several other central and western states began using the criterion on an experimental basis. Ferree said based on the results, the change was mandated nationwide.

In a prepared statement, Ferree said the decision to increase the size of hail for thunderstorm warnings was research-based.

"Significant damage does not occur until hail size reaches 1 inch (quarter-size) in diameter," Ferree said. By increasing the size of hail required for a weather service warning, officials said they expect residents to pay more attention to thunderstorm warnings based on hail.

"The frequency of severe thunderstorm warnings issued for penny-size and nickel-size hail might have desensitized the public to take protective action during a severe thunderstorm warning," Ferree said. With the larger-size hail, "warnings carry more weight."

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