I know the criterium to initiate a severe thuderstorm warning is 3/4 inch hail or winds of 58mph. With as many people killed by lightning and the implementation of lightning detection systems, why hasn't (or will) the NWS include lightning as an aspect for designating a thunderstorm as severe?
Posted July 18, 2007
MIKE MOSS SAYS: Ryan, The basic reason for not including lightning as a crieria for severe thunderstorm warnings is that, unlike large hail and damaging winds, every thunderstorm, by definition, produces lightning. For that reason, every thunderstorm carries the danger of lightning strikes and a warning would in effect be redundant. If thunderstorms are in the forecast, lightning is already expected. Likewise, if one hears thunder then you know that lightning is present, whereas the occurence of lightning and thunder doesn't necessarily mean that large hail and dmaging winds are occurring or will occur.
It would likely dilute the watch and warning program if every occurrence of a thunderstorm of any kind resulted in the issuance of a warning. This is already a concern to the National Weather Servie and to those of us in the media, because of the 3/4" (roughly penny size) hail criteria. Many storms produce a small area of penny to nickel size hail and result in severe thunderstorm warnings for that reason alone, but it is rare that any significant property damage and extremely rare that any injuries result from hail of this size, so the frequent warnings already create a bit of a "numbness" on the part of the public that makes it a little less likely that people will take a given warning as seriously as they should. Warnings due to lightning might exacerbate this effect even further. Do note that the NWS will sometimes issue a "Special Weather Statement" to highlight storms or storm complexes that are producing especially high lighning rates.