CASPER, Wyo. — The National Weather Service in Riverton says that starting Monday, Aug. 2 any thunderstorms deemed in the “destructive” category will activate “Wireless Emergency Alerts” on smartphones.
“Criteria for a destructive threat is at least 2.75 inch diameter hail and/or 80 mph thunderstorm winds,” the NWS in Riverton says.
The National Weather Service says that severe storms can be life-threatening but they are not all the same.
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“Hazardous conditions range from tornadoes, large hail storms, and widespread straight-line winds called derechoes, to cloud-to-ground lightning and flash flooding,” the NWS says. “Starting August 2, the National Weather Service will better convey the severity and potential impacts from thunderstorm winds and hail by adding a ‘damage threat’ tag to Severe Thunderstorm Warnings, similar to our Tornado and Flash Flood Warnings.”
The NWS has developed three categories of damage threat for severe thunderstorm warnings: destructive, considerable and base.
“These tags and additional messaging are designed to promote immediate action, based on the threats,” the NWS says.
- destructive damage threat: 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.
- considerable damage threat: at least 1.75 inch diameter (golf ball-sized) hail and/or 70 mph thunderstorm winds. This will not activate a WEA.
- baseline or “base” severe thunderstorm warning: 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.
About 10% of all severe storms reach the destructive category each year, according to the NWS.
“Most of these storms are damaging wind events such as derechoes and some of the larger, more intense thunderstorms, called ‘Supercell’ storms that can typically produce very large hail in their path,” the NWS says. “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. 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 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.”
The NWS adds that the “22 costliest weather disasters in 2020 were severe thunderstorms.” The destructive category would have activated the Wireless Emergency Alerts for many of these storms, the costliest of which was a derecho that affected Iowa in August 2020, causing $11 billion in damages.
“Learn how to stay safe in a severe thunderstorm. Knowing what to do before, during, and after severe weather can increase your chances of survival,” the NWS says. “The NOAA Storm Prediction Center provides forecasts of severe weather up to seven days in advance, and severe thunderstorm and tornado watches several hours before storms form. Explore our Severe Weather 101 webpage.”