A new rubric to classify severe thunderstorm threats went into effect this month, with a focus on assessing potential hail and wind damage.

According to a National Weather Service (NWS) press release, a category for “damage threat” has been added to Severe Thunderstorm Warnings.

“We developed three categories of damage threat for Severe Thunderstorm Warnings,” the release said. “The categories, in order of highest to lowest damage threat, are destructive, considerable and base. These tags and additional messaging are designed to promote immediate action based on the threats.”

• Destructive: storms with 2.75-inch diameter hail and 80 mph winds
• Considerable: storms with 1.75-inch diameter hail and 70 mph winds
• Base: storms producing 1-inch (quarter-sized) hail and 58 mph winds

Only storms in the worst category (destructive) will trigger an emergency smartphone alert, the weather bureau said.

The destructive category is meant to warn the public about derechos or supercells that can produce large hail and damaging winds. Only about one in 10 storms reach this level.

“The new destructive thunderstorm category conveys to the public urgent action is needed, a life-threatening event is occurring and may cause substantial damage to property,” the release said.

All National Weather Service Severe Thunderstorm Warnings will continue to be issued and distributed via weather.gov, NOAA Weather Radio, the Emergency Alert System and through dissemination systems to our emergency managers and partners. The addition of damage threat tags are part of the broader Hazard Simplification Project to improve communication of watches and warnings to the public.

Learn more about storm safety by visiting the NWS’s Severe Weather 101 webpage.