Fresno, California 2021-07-30 11:02:23 –
Heavy thunderstorms can be life-threatening, but not all heavy thunderstorms are the same.
Dangerous conditions range from tornadoes, large hailstorms, widespread linear winds called derechos, to lightning from clouds to the ground and flash floods.
According to the National Weather Service, the new alert can better communicate the seriousness and potential impact of thunderstorm winds and hail by adding a “damage threat” tag similar to tornado and flash flood warnings. ..
Currently, there are three categories of threats of Severe Thunderstorm damage, from highest to lowest, destructive, significant, and basic.
These tags and additional messaging are designed to facilitate immediate action based on threats.
The criteria for a catastrophic threat are hail and / or thunderstorm winds at least 2.75 inches (baseball size) in diameter and / or 80 mph.
Alerts with this tag automatically activate wireless emergency alerts (WEA) on smartphones in the alert area.
The criteria for serious damage threats are hail and / or thunderstorm winds at least 1.75 inches (golf ball size) in diameter and / or 70 mph.
This does not activate WEA.
The baseline or “base” heavy thunderstorm warning criteria have not changed. 1.00 inch (1/4 size) hail and / or 58 mph thunderstorm wind.
This also does not activate WEA.
If the damage threat tag is not present, the damage is expected to be at the base level.
Nationally, each year, only 10% of all heavy thunderstorms reach the destructive category.
Most of these storms damage wind events such as derecho, and some of the larger and heavier thunderstorms called “supercell” storms can usually produce very large hail in their path. I have.
The new catastrophic thunderstorm category informs the public that urgent action is needed, and life-threatening events are occurring that can cause serious property damage.
All National Weather Service thunderstorm alerts will continue to be issued and distributed via weather.gov, NOAA weather radio, emergency alert systems, and distribution systems to emergency managers and partners.
The addition of damage threat tags is part of a broader hazard simplification project to improve surveillance and alert transmission to the general public.
Thirteen of the 22 most expensive weather disasters in 2020 were heavy thunderstorms. The new “destructive” tag activates wireless emergency alerts for many of these influential events, including the most expensive thunderstorm in U.S. history and the $ 11 billion derecho that hit Iowa in August 2020. To
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New ‘Destructive’ Severe Thunderstorm Warning category to trigger wireless Emergency Alerts on mobile phones Source link New ‘Destructive’ Severe Thunderstorm Warning category to trigger wireless Emergency Alerts on mobile phones