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Weather Service’s tornado warnings were delayed during deadly Iowa outbreak

Because of dissemination problems, some warnings didn’t reach the public until seven minutes after they were issued

Cleanup efforts are underway in Winterset, Iowa, on Sunday after a tornado had torn through the area. (Bryon Houlgrave/Des Moines Register/AP)
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Seven people are dead following an onslaught of tornadoes across Iowa on Saturday. Amid the life-threatening weather, a dissemination problem at the National Weather Service meant tornado warnings were delayed in reaching the public.

A total of 17 tornado warnings were issued by the National Weather Service in Des Moines on Saturday. Tornado warnings, which connote an immediate threat to life from a tornado and urge sheltering, trigger wireless emergency alerts that notify residents of incoming danger.

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However, up to seven minutes elapsed between the time meteorologists at the Weather Service issued warnings and when the public could access them, potentially shortening or eliminating the window for taking action.

“The local offices were issuing the products in a timely fashion, but a dissemination delay affecting all [Weather Services] offices nationwide caused the products to be transmitted a number of minutes later,” Daryl Herzmann, a systems analyst with Iowa State University, said in an email. He created a popular site used by meteorologists that archives National Weather Service advisories, watches and warnings.

Jonathan Porter, senior vice president at AccuWeather, wrote in an email that the delays were “very problematic” since people rely on government warnings to take action. “These delays may have contributed to complexities in how people and businesses reacted to the immediate tornado threat in the affected communities,” he said.

Susan Buchanan, the Weather Service’s director of public affairs, wrote on Sunday that “a technical issue caused a delay of between 2-7 minutes for some transmissions,” noting that “system engineers quickly took action as soon as the problem was detected.” She emphasized that warning lead times averaged approximately 20 minutes during the outbreak, well above the national average of 10 minutes.

In a follow-up statement Monday, Buchanan said the communications delay resulted from a damaged fiber optic cable at the Weather Service’s Dallas-Fort Worth office.

“The cable outage caused that office to switch from its primary, land-based communication network to a backup satellite-based network that serves every NWS field office,” she wrote. “The uptick in messages flowing to the central message handler from NWS Central Region offices due to the severe weather, combined with the performance characteristics of the satellite network in use at a co-located site, slowed down the queue of message transmissions and created a brief backlog across multiple offices.”

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Herzmann wrote that the “issue started at about 2:15 p.m. CST and lasted until about 6:10 p.m. CST,” coinciding with the peak of the tornado event.

The Des Moines Weather Service issued its first tornado warning at 3:22 p.m. Central time; it was delayed by 2 minutes and 47 seconds, according to Herzmann.

As the tornadic storms intensified, the delays in warning dissemination grew.

At 4:11 p.m. Central time, the Weather Service was sounding the alarm about a “confirmed tornado … located near Green Valley Lake,” but it took 9 minutes and 17 seconds for that alert to be broadcast, Herzmann found. The Weather Service said the maximum delay was closer to seven minutes. That was the same storm that would kill six people near Winterset in Madison County, including two children younger than five, just over 20 minutes later.

At 4:34 p.m., a downwind warning was issued for the Winterset tornado, which five minutes later the Weather Service would call “confirmed large and extremely dangerous.” It took nearly six minutes for that alert to reach the public, however, Herzmann found.

The Des Moines Weather Service, aware of the issue, took to social media to tweet warnings and notified local television stations. But unless the public was tuned to Twitter or their televisions sets, they wouldn’t have known about the warnings on time.

Problems continued as the tornado passed through southeastern parts of the Des Moines metro area and approached Interstate 80, with delay times ranging between four minutes and seven minutes, according to Herzmann.

“I don’t know if this impacted Weather Radio, but every other dissemination vehicle was impacted,” Herzmann wrote.

The Weather Service office in Des Moines rated the tornado that struck Winterset as an EF4 on the 0 to 5 scale for tornado intensity, the strongest to strike Iowa since 2013. It declined to speak on the dissemination issue.

“There were known issues with dissemination, the details of which are available with National Weather Service public affairs,” Alex Krull, meteorologist with the Des Moines office, said in a phone call.

National Weather Service Central Operations in College Park, Md., didn’t inform core partners about the issue until 5:43 p.m. Central time — hours after the problem began — at which point the killer tornado had already razed a swath from Winterset to Interstate 80.

Herzmann and others were concerned about what impact the delays may have had during the outbreak.

“I am sick that the local offices had to deal with this and what implications it may have had for those in the path of the tornadoes yesterday,” he tweeted on Sunday. Others echoed his sentiment.

“This is beyond unacceptable & is becoming more common,” tweeted Rob Lightbown of Crown Weather Service, a private forecasting company, who referenced a similar outage last week that prevented snow squall warnings in the Northeast from going out to the public correctly. During that episode, television meteorologists were forced to manually draw boxes on maps, since National Weather Service shapefiles didn’t display.

“Tornado warnings were delayed getting to the public yesterday during a killer tornado event,” tweeted Greg Diamond, a meteorologist and weather producer for Fox Weather. “This is a huge problem.”

In the wake of the incident, the Weather Service’s “primary goal now is to immediately implement procedural changes to avoid a repeat,” Buchanan wrote. “One short-term option under consideration would move to the use of service backup by another forecast office in this type of situation, rather than the satellite-based backup, to prevent message build ups.”

The Weather Service has been plagued by technical infrastructure problems in recent years, with regular issues that obstruct the access of certain products and ease of communications, including during high-end weather events.

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Websites briefly went down for some users during the height of last year’s severe weather season, and NWS Chat — a chatroom used by emergency management and broadcast entities to connect with Weather Service meteorologists — kicks users out when the system becomes clogged.

During a rare “high risk” tornado outbreak on March 15, 2021, the National Weather Service in Birmingham announced it would be reverting to the instant messaging software Slack instead of relying on NWS Chat. The office was reprimanded by Weather Service headquarters and forced it to use NWS Chat.

Significant technical issues within the Weather Service information dissemination date back to at least 2013.

Saturday’s warning delay “is another example in a series of situations where the NWS core data dissemination systems have experienced failures or serious degradation during severe weather events — when they are needed most,” AccuWeather’s Porter wrote. “A chain is only as strong as its weakest link — and right now the data dissemination capabilities of the NWS are a weak link, which is a major public safety concern.”


An earlier version of this article incorrectly said NOAA weather radio was inaccessible in west-central Iowa during Saturday's tornado event. The National Weather Service said that, while the radio had a communications failure on Friday, service was restored on Saturday even though the agency did not issue a return-to-service statement. The article has been corrected.