New categories added to severe thunderstorm warnings


All severe thunderstorms can be life threatening, but not all severe storms are the same. On Tuesday, August 3rd, the National Weather Service implemented a better way to try and help convey the associated risks and impacts from thunderstorm winds and hail by adding a ‘damage threat’ tag to all Severe Thunderstorm Warnings. This is similar to the tags that are currently on Tornado Warnings and Flash Flood Warnings. Currently, tornado and flash flood warnings were the only warnings that triggered a WEA (Wireless Emergency Alert).

There will now be three (3) categories to highlight the potential risks associated with a severe thunderstorm: base, considerable and destructive. Severe thunderstorm hazards range from tornadoes, large hail, widespread straight-line wind damage, cloud to ground lightning and flash flooding. The new tags to the warnings were implemented to promote immediate action based on the threat and severity of the storm.

The criteria for a ‘base’ severe thunderstorm warning remains unchanged – quarter-sized (one inch) hail and/or 58 mph thunderstorm wind gusts. When no damage threat tag is present with the warning, the damage is expected to be at the base level. A ‘considerable’ damage threat tag is added when a severe storm is capable of producing at least golf ball sized hail (1.75 inches) and/or 70 mph thunderstorm wind gusts. This will not activate a WEA (Wireless Emergency Alert). A ‘destructive’ damage threat tag is added when a severe storm is capable of baseball sized hail (2.75 inches) and/or 80 mph thunderstorm wind gusts. The August 10th, 2020 derecho would be an example where the ‘destructive’ damage threat tag would have been used. This WILL automatically activate a WEA on all smartphones within the warned area. These changes have gone into effect immediately and will be used now for all severe thunderstorm warnings going forward.

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