REGIONAL — Starting August 2, 2021, severe thunderstorms that are deemed “destructive” by the U.S. National Weather Service (NWS) will activate a Wireless Emergency Alert (WEA) on smartphones.
According to a July 22 news release from the NWS, severe thunderstorms can be life-threatening, but not all severe storms are the same. Hazardous conditions range from tornadoes, large hail storms, and widespread straight-line winds called derechos, to cloud-to-ground lightning and flash flooding.
The NWS developed three categories of damage threat for Severe Thunderstorm Warnings. 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 threat.
“Destructive” and “Considerable” Damage Threat Categories
- 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.
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, can typically produce very large hail in their paths.
The new destructive thunderstorm category conveys to the public that urgent action is needed, a life-threatening event is occurring and may cause substantial damage to property. Storms categorized as destructive will trigger a WEA to your cell phone.
All of the NWS Thunderstorm Warnings will continue to be issued and distributed via the NWS website, NOAA Weather Radio, Emergency Alert System and through dissemination systems to the NWS’s emergency managers and partners. The addition of damage threat tags are part of a broader Hazard Simplification Project to improve communication of watches and warnings to the public.
Thirteen of the twenty-two 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.
For more information on what do to during any of these storms and how to stay safe, click here.