|
The
two damage threat categories will depend on hail size and wind
speeds.
A “considerable threat” is a storm with golf ball-sized hail and
wind speeds of 70 miles per hour or greater, and a “destructive
threat” warning is a storm with baseball-sized hail and 80
mile-per-hour winds or greater.
“The difference between 58-60 mph winds and 90 mph winds like we
saw in the derecho last year, that makes a pretty large
difference,” said Illinois Climatologist Trent Ford.
The billion-dollar August 10, 2020, Midwest Derecho is an
example of when the thunderstorm damage threat from high winds
would be classified as “destructive” in severe thunderstorm
warnings.
The storm tracked across eastern Iowa into Illinois with winds
of up to 140 mph. Widespread damage to buildings was reported,
and millions of acres of crops were damaged or destroyed.
Winds estimated at 100 mph impacted Princeton, Illinois in
Bureau County where a 150-foot communications tower collapsed
and numerous power poles were snapped. Long-duration power
outages occurred across the region.
If a destructive threat severe thunderstorm warning is issued, a
new alert will be sent out.
“The storms that are classified as that by the National Weather
Service will automatically trigger a Wireless Emergency Alert,
or a WEA, and that is an alert that goes directly to smartphones,”
Ford said.
This emergency alert will be accompanied by a loud screech that
will alert you when a particularly dangerous severe weather
threat is in your area. Other warnings already trigger a
Wireless Emergency Alert to phones, including tornado warnings
and higher-end flash flood warnings.
According to the NWS, only 10% of all severe thunderstorms reach
the “destructive” criteria each year across the country.
|
|
