Tornado warnings delayed during deadly Iowa outbreak

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.

However, up to nine 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 service] 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.

Susan Buchanan, the weather service’s director of public affairs, wrote 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 about 20 minutes during the outbreak.

“The National Weather Service is investigating this issue to determine the root cause and prevent it from happening in the future,” she wrote.

Problems started midafternoon Saturday

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 office issued its first tornado warning at 3:22 p.m. Central time; it was delayed by 2 minutes and 47 seconds.

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. That was the same storm that would kill six people near Winterset in Madison County, including two children younger than 5, 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.

The Des Moines weather service office, 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 were affected by the dissemination delays.

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.

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

Weather radio was inaccessible in west-central Iowa as the transmitter tower in Denison, Iowa, suffered a “communications failure” Friday that knocked it “off the air.” There was no word of the transmitter being back online by Sunday.

The weather service office in Des Moines was still surveying the damage from the tornado in Winterset on Sunday evening, which will be rated at least EF3 on the 0 to 5 scale for twister intensity, corresponding to maximum winds of at least 136 mph. 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.

“This is beyond acceptable”

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.

Other technical issues at weather service

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

Websites briefly went down for some users during the height of last year’s severe weather season, and NWS Chat — a chat room 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, which reportedly suffered a litany of issues during the next outbreak.