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NWS makes important change to Severe Thunderstorm Warnings

The National Weather Service has made changes to Severe Thunderstorm Warnings to better convey severity and potential impacts.

JACKSONVILLE, Fla. — We all know, especially living on the First Coast, not all severe storms are the same. Severe thunderstorms can be life-threatening. Hazardous conditions range from tornadoes to hail, widespread straight-line winds to dangerous lightning, and even flash flooding.

And now, the National Weather Service has a new way to better convey the severity and potential impacts from thunderstorms. They’ve added a “damage threat” tag to Severe Thunderstorm Warnings, similar to what is already done with Tornado and Flash Flood Warnings. This change took effect on Monday, August 2.

The NWS developed three categories of damage threat for Severe Thunderstorm Warnings. The categories, ranked in order from highest to lowest damage threat, are 1) destructive, 2) considerable, and 3) base. These tags and additional messaging are designed to promote immediate action, based on the threats.

  • The criteria for a destructive damage threat is at least 2.75 inch diameter (baseball-sized) hail and/or 80 mph thunderstorm winds. Warnings with this tag will automatically activate a Wireless Emergency Alert (WEA) on smartphones within the warned area.
  • The criteria for a considerable damage threat is at least 1.75 inch diameter (golf ball-sized) hail and/or 70 mph thunderstorm winds. This will not activate a WEA.
  • The criteria for a baseline or “base” severe thunderstorm warning remains unchanged, 1.00 inch (quarter-sized) hail and/or 58 mph thunderstorm winds. This will not activate a WEA. When no damage threat tag is present, damage is expected to be at the base level.

What is the chance we’ll see one of these “destructive” damage threat tags across the First Coast? Low, according to our First Coast News Weather Team and meteorologists at Jacksonville’s National Weather Service office, but it’s still important to understand for if and when they are issued in the area.

On average, only 10 percent of all severe thunderstorms reach the destructive category each year, nationwide. Most of these storms are damaging wind events such as derechos and some of the larger, more intense thunderstorms, called “Supercell” storms that can produce very large hail in their path.

The new destructive thunderstorm category conveys urgent action is needed, a life-threatening event is occurring and may cause substantial damage. Storms categorized as destructive will trigger a WEA to your cell phone.

All National Weather Service Severe Thunderstorm Warnings will continue to be issued and distributed via weather.gov, NOAA Weather Radio, Emergency Alert System and through dissemination systems to our emergency managers and media 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.

Thirteen of the 22 costliest weather disasters in 2020 were severe thunderstorms. The new “destructive” tag would have activated a Wireless Emergency Alert for many of these impactful events, including the costliest thunderstorm in U.S. history, the $11 billion derecho that affected Iowa in August 2020.

Explore NWS’s Severe Weather 101 webpage.