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posted: 7/4/2020 6:20 AM

Destructive thunderstorm winds and hail could soon trigger alerts to your cellphone

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  • The roof of the Sonic Drive-In in Brookhaven, Miss., was damaged in April after severe weather.

    The roof of the Sonic Drive-In in Brookhaven, Miss., was damaged in April after severe weather.
    (Gracie Byrne/The Daily Leader via AP, April 2020)

 
 

On April 19, cellphones did not sound when violent 70- to 90-mph thunderstorm winds rocked the central and southern part of Alabama. RVs were toppled, as wind-driven hail destroyed siding and shattered windows. Trees were downed like dominoes, and power line damage occurred in a widespread area. A 61-year-old man died in the town of Wiregrass when his trailer was flipped by the strong winds.

For years, meteorologists have expressed concern about the lack of special alerts for the most dangerous thunderstorm situations. Tornado and flash flood warnings are sent to cellphones via wireless emergency alerts but not severe thunderstorm warnings.

But there's now a plan to change this.

On Tuesday, the National Weather Service proposed a new tiered system for severe thunderstorms, with the most extreme storms, containing winds of at least 80 mph and/or baseball-sized hail, activating wireless emergency alerts. Less intense storms, containing winds of at least 58 mph and quarter-sized hail, would still trigger storm warnings but would not emit a high-pitched tone on your phone.

Historically, all severe thunderstorms -- regardless of intensity -- have been treated equally by the NWS. But a low-end severe thunderstorm with isolated gusts to 58 mph has impacts far less extreme than a violent storm complex like a derecho that can produce widespread gusts over 70 mph.

The majority of storm warnings are issued for the lower-end storms which, in many locations, occur frequently. For example, severe thunderstorm warnings were issued 500 times in 2019 by the Washington-Baltimore NWS office.

They're so common and can affect such small areas that some people tune them out.

"Severe thunderstorm warnings are routinely ignored by the public, and honestly, most broadcasters," wrote Josh Johnson, chief meteorologist at WSFA in Montgomery, Ala., in a Twitter message. "The typical storm that prompts a severe thunderstorm warning creates small areas of hail and wind. And this wind and hail affect a very small percentage of the people in that warning."

Johnson, who covered the destructive April 19 storm outbreak in his state, worries the frequent issuance of warnings for highly-local storms undermines the seriousness of severe thunderstorm warnings when widespread high-end winds or large hail are imminent.

For the storms on April 19 that raked his viewing area, "we had an intense wind signature in a line of severe thunderstorms," he recalled. "We broke into programming and stayed on continuously for hours, tracking it across southeast Alabama. It produced 70-90 mph wind gusts and large swaths of significant damage. So, is that situation really the same as a pulse thunderstorm that might produce quarter-sized hail? No, of course not. But we treat it the same way. We lump those two situations together under the 'severe thunderstorm' mantle. It doesn't fit."

Some forecasters have tried to get creative during those kind of extreme events, even breaking NWS protocol. The NWS office in Cheyenne, Wyo., attached the phrase "severe thunderstorm emergency" to a warning it issued on Aug. 16, 2019 due to the likelihood of baseball-sized hail near Scottsbluff, Neb.

"We at the time ... had concern for the folks of Scottsbluff," said Rob Cox, science and operations officer at the National Weather Service in Cheyenne. "We had one storm that went right through after another, and they were both big hailstorms. We ... wanted the public to realize 'this is a critical situation, you need to be aware that those who had vulnerabilities after the first storm are more at risk.'"

National Weather Service policy does not currently permit the issuance of severe thunderstorm emergencies. But the proposed tiered system aims to give forecasters a new tool to convey the urgency of the most extreme storms.

"This added capability is aimed at promoting instant and immediate life preservation actions for this level of hail and/or wind threat," the proposal states.

The National Weather Service has been working toward implementing tiered severe storm warnings for quite some time.

"This has been long in the works," said Greg Schoor, severe weather program lead at the NWS. "One would think this was very easy to do, but we had to think through a lot of different elements to even get to this proposal."

The warnings will get a facelift, modeled after the adjustments made to tornado warnings and flash flood warnings that began in 2013 and rolled out nationwide by 2018. Those warnings were converted into "impact-based" products, emphasizing the consequences posed by an impending hazard rather than just the nature of the threat itself.

"The format we had for tornado warnings, we now have down pat," said Schoor. "That's the way we want it to be."

Tornado warnings and flash flood warnings now have levels that are reflected in the wording of the warning and the call to action items included. The same will hold true for severe weather thunderstorms if this proposal is implemented.

Schoor estimates that only about 2 percent of all severe thunderstorm warnings will reach the "destructive" level necessary to trigger a wireless emergency alerts but hopes they motivate people to take action.

The proposed tiered system not only includes specific language and calls to action for the low-end and high-end severe storms, but also for those that fall in between.

Schoor said it was important to provide some middle ground. Thunderstorms predicted to produce golf ball size hail or 70 mph winds will be labeled as a "considerable threat" in the proposed system but won't activate wireless emergency alerts.

The first step toward putting the proposed changes into action comes from soliciting public comment. Schoor and his colleagues at the National Weather Service rolled out a public information statement on June 30 inviting feedback which can be submitted through July 31 here.

"Everything is in proposal mode of course until we get the service change notice out," said Schoor. "Once we get public comment back ... and we make sure there's not a running theme, let's say no showstoppers ... we'll send out service change notice to local National Weather Service offices."

From there, a 75-day period will begin during which the 122 local weather forecast offices review the notice and offer their thoughts.

"Then we're talking about probably fall before that's over," said Schoor. "We might have a 'turn on' date at the end of this year or maybe sooner. It may be into next year, hopefully by January."

Schoor hopes the changes will be made in time to roll them out before next spring's severe weather season and that all NWS offices will be able to enact the changes simultaneously.

"We're going to try to do as much of a 'flip the switch' as we can," said Schoor.