National Weather Service Changes Severe Storm Qualifications Effective January 5, 2010.
Because significant damage does not occur until hail size reaches 1-inch in diameter, the National Weather Service has upped hail size from .75in to 1.0in in NWS-issued Severe Thunderstorm Warnings. The NWS reports that user feedback suggests warnings are now more meaningful. TV networks participating in early experiments reported that they had to break into regularly scheduled programming less often with the new criteria. No other severe thunderstorm criteria will change.
What is a severe thunderstorm?