Wednesday, May 27, 2009
Weather columnist Kevin Myatt: Hail criterion changing for severe thunderstorms
Kevin Myatt is The Roanoke Times' weather columnist.
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It will become a little harder for a thunderstorm to be considered severe in 2010.
The National Weather Service's Eastern Region -- which includes its office in Blacksburg -- is adopting a new rule that hail size of 1 inch makes a storm severe, an increase over the three-quarter-inch requirement currently in effect.
The 1-inch criterion has been tested in other weather service regions in previous years.
A storm is also considered severe if it has 58 mph winds or greater. That requirement isn't changing.
It is important to note that the wind and hail requirements are "either/or," not "both/and." If either the wind or hail requirement is met by ground observation, or if there is a strong expectation of the hail or wind requirement being met based on Doppler radar, a severe thunderstorm warning is issued.
The net effect is likely to be that fewer severe thunderstorm warnings will be issued. Some people feel as if there are too many such warnings, and therefore the warnings often get ignored.
The weather service is also issuing warnings for more narrow geographic areas, often parts of counties rather than entire counties, with specific communities affected named in the warnings.
It's all an effort at greater precision, and to make the warnings meaningful for the public.
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