New “Destructive” Severe Thunderstorm Warning Category Mobile Phone Alerts


screenshot of thunderstorm mobile alert

July 22, 2021 – Extreme thunderstorms may be life-threatening, however not all extreme storms are the identical. Hazardous situations vary from tornadoes, giant hail storms, and widespread straight-line winds known as derechoes, to cloud-to-ground lightning and flash flooding. Beginning August 2, the Nationwide Climate Service will higher convey the severity and potential impacts from thunderstorm winds and hail by including a “injury risk” tag to Extreme Thunderstorm Warnings, just like our Twister and Flash Flood Warnings.

“Damaging” and “Appreciable” Injury Menace Classes

We developed three classes of harm risk for Extreme Thunderstorm Warnings. The classes, so as of highest to lowest injury risk, are damaging, appreciable, and base. These tags and extra messaging are designed to advertise speedy motion, based mostly on the threats.

  • The standards for a damaging injury risk is at the very least 2.75 inch diameter (baseball-sized) hail and/or 80 mph thunderstorm winds. Warnings with this tag will robotically activate a Wi-fi Emergency Alert (WEA) on smartphones inside the warned space.
  • The standards for a substantial injury risk is at the very least 1.75 inch diameter (golf ball-sized) hail and/or 70 mph thunderstorm winds. This won’t activate a WEA.
  • The standards for a baseline or “base” extreme thunderstorm warning stays unchanged, 1.00 inch (quarter-sized) hail and/or 58 mph thunderstorm winds. This won’t activate a WEA. When no injury risk tag is current, injury is predicted to be on the base degree.

On common, solely 10 p.c of all extreme thunderstorms attain the damaging class every year, nationwide. Most of those storms are damaging wind occasions similar to derechoes and among the bigger, extra intense thunderstorms, known as “Supercell” storms that may usually produce very giant hail of their path. The brand new damaging thunderstorm class conveys to the general public pressing motion is required, a life-threatening occasion is happening and should trigger substantial injury to property. Storms categorized as damaging will set off a WEA to your cellphone.

All National Weather Service Extreme Thunderstorm Warnings will proceed to be issued and distributed by way of, NOAA Climate Radio, Emergency Alert System and thru dissemination techniques to our emergency managers and companions. The addition of harm risk tags are a part of the broader Hazard Simplification Challenge to enhance communication of watches and warnings to the general public.

13 of the 22 costliest climate disasters in 2020 had been extreme thunderstorms. The brand new “damaging” tag would have activated a Wi-fi Emergency Alert for a lot of of those impactful occasions, together with the most expensive thunderstorm in U.S. historical past, the $11 billion derecho that affected Iowa in August 2020.

Learn to keep protected in a extreme thunderstorm. Understanding what to do earlier than, throughout, and after extreme climate can enhance your probabilities of survival.

The NOAA Storm Prediction Heart supplies forecasts of extreme climate as much as seven days prematurely, and extreme thunderstorm and twister watches a number of hours earlier than storms kind.


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