Beginning on July 28th, 2021, Severe Thunderstorms that are deemed “Destructive” will activate a Wireless Emergency Alert (WEA) on smartphones. The criteria for a severe thunderstorm to be deemed a “destructive threat” is at least 2.75″ size hail (baseball size) and or 80 MPH thunderstorm winds. The graphic below demonstrates what the WEA message will look like.
The National Weather Service has developed three categories of damage threat for Severe Thunderstorm Warnings to distinguish between high-impact and low-impact events. 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. Details on these tags are listed below.
- The criteria for the 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, the damage is expected to be at the base level.
According to the National Weather Service, on average, only about 10% of all severe thunderstorms reach the destructive category each year nationwide. Most of those 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 path. 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.