Two brutal rounds of supercell thunderstorms left multiple trails of destruction across the southern and central Great Plains from Friday afternoon into early Sunday morning, April 26-28, in one of the region’s most prolific and damaging tornado outbreaks in years. The most concentrated activity ran through eastern Nebraska and western Iowa on Friday and from northwest Texas to southwest Missouri on Saturday.
At least four tornado-related deaths had been reported as of Sunday night, including one in Iowa and three in Oklahoma. Despite these fatalities, a slew of prompt warnings from the National Weather Service — particularly the hyper-slammed offices in Omaha, Nebraska, and Norman, Oklahoma — appear to have saved lives and kept many other people safe from harm.
Both the Omaha and Norman offices set their respective records for the most number of tornado warnings issued in a day, with 42 and 59 respectively.
There were no more than three dozen people hurt in Nebraska and Iowa in the first round of tornadoes, and most of those injuries were minor, according to officials cited by the Omaha World-Herald. One man in hard-hit Minden, Iowa, died of his injuries over the weekend. Preliminary ratings of the Nebraska and Iowa tornadoes are expected on Monday. A number of private planes were damaged or destroyed at Omaha’s main airport, Eppley Airfield.
With relatively little wraparound rain affecting visibility, many of the Nebraska/Iowa twisters were sharply evident (and stomach-churning on video).
The human toll was higher in Oklahoma on Saturday as the day’s worst tornadoes struck well after dark, when visibility is worse and when public vigilance might have ebbed somewhat. As of early Monday, The Daily Oklahoman had reported four fatalities, including two deaths in Marietta, one in Holdenville, and one in Sulphur. More than 100 people were injured, according to state officials cited by the Oklahoman.
Much of downtown Sulphur, a resort town next to the Chickasaw National Recreation Area, was severely damaged, and the tornado laid waste to a huge Dollar Tree distribution center in Marietta. The tornadoes in Sulphur and Marietta earned preliminary ratings of at least EF3 on Sunday, with more investigation to come. Update (2 pm EDT Monday): The Marietta tornado has been upgraded to EF4, while surveying continues on the Sulphur tornado.
The Great Plains return to tragic form as a tornado factory
Many of the worst tornado outbreaks in recent years have plagued the Mississippi Valley and the Southeast U.S., in line with an eastward shift in tornado production over the past 40-plus years that’s projected to continue with climate change.
In contrast, this weekend’s outbreak was notable in that it focused its wrath on the “classic” Tornado Alley of the Great Plains, from north Texas into western Iowa.
The corridors hardest hit on Friday and Saturday were both amply pegged by the Day 4 and Day 5 severe weather outlooks issued by the Storm Prediction Center on Tuesday, April 23. Enhanced risk areas (level three of five), both of which explicitly noted the danger of strong tornadoes, were included in Day 2 outlooks issued by the center more than 24 hours ahead of the Friday storms across eastern Nebraska and western Iowa and more than 24 hours before the Saturday storms from Texas to Missouri.
Two tornado emergencies — the most dire type of tornado warning, reserved for cases where “a severe threat to human life exists and catastrophic damage is imminent or occurring” — were issued by the NWS/Omaha office, one for the western fringes of the Omaha area and another for the Minden tornado.
As it happens, this Friday, May 3, is the 25th anniversary of the first-ever tornado emergency, which was issued on the fly ahead of a violent twister (later to be rated EF5) that was approaching the Oklahoma City area. That long-track tornado on May 3, 1999, became the nation’s first to produce at least $1 billion in damage as it killed 46 people, injured some 800 more, and damaged roughly 8,000 buildings. (For more on the evolution of tornado emergencies, see my article with Ashton Robinson Cook, published on Monday for members of the AMS Weather Band, a group for weather enthusiasts. Weather Band articles are normally restricted to members, but this one is being made freely available by AMS.)
Two outbreaks or one?
After filtering out duplicates, the NOAA/NWS Storm Prediction Center tallied preliminary totals of 86 tornadoes from late Friday into early Saturday, with another 39 filtered reports from Saturday afternoon until just after midnight. These bursts of activity were separated by about 14 tornado-free hours, which by some strict definitions would qualify the event as two outbreaks instead of one.
However, the same upper-level storm and frontal system drove both of the swarms of activity, and there was considerable overlap in the severe weather areas on the two days (see Figure 1 below), so it’s reasonable to see these as dual outgrowths of the same event. A 2021 overview led by Paulina Ćwik in the Bulletin of the American Meteorological Society asserts that “there is no one consistent, unequivocal definition of a tornado outbreak — nor, we believe, should there be.”
Winds over 200 mph measured by Doppler on Wheels
As shown in the embedded tweet above, a Doppler on Wheels unit sampled winds of around 224 mph near Harlan, Iowa, in the tornado that moved through Minden. Damage that qualifies for an EF5 rating — which was last applied to a tornado in Moore, Oklahoma, on May 20, 2013 — implies surface winds of at least 200 mph. However, the Doppler on Wheels measurement was collected at an altitude of close to 1,000 feet, where winds are less affected by surface friction and can be considerably stronger than near ground level. The standard height of routine wind measurements is 10 meters or 33 feet.
Read: It’s been a record-long time since the last EF5 tornado
Moreover, the Enhanced Fujita [EF] Scale is specifically a damage scale. An EF rating can only be inferred from a broad set of damage indicators, such as a well-built home being swept clean from its foundation, rather than from remotely sensed wind data (although such reports can be provided as supplemental data, a practice that’s now being codified in a major multiyear update to the EF scale now in process).
It’s also important to note that even an EF3 tornado can cause a stunning amount of destruction, especially if it has a large, long-lived circulation and/or if a number of buildings lack the reinforcements needed to minimize tornado damage. At the same time, even a tornado with winds over 200 mph wouldn’t get an EF5 rating if it moved only through a barren field. Like a tree falling in the forest that nobody hears, if a twister damages nothing strong enough to yield an EF5 rating, then it can’t be rated EF5.
Tornadic storm kills 5 in Guangzhou, China
While many tornado-aware Americans watched the Plains outbreak unfold, one of the world’s largest urban areas experienced its own deadly tornado. This short-lived but destructive twister tore into Guangming Village in the Baiyun District of Guangzhou, China, on Saturday afternoon local time. According to the Associated Press, the tornado caused five deaths and 33 injuries and damaged more than 140 buildings. Massive hail up to 4.72 inches in diameter was also reported from the storm.
Sitting on the Chinese mainland just across from Hong Kong, the Guangzhou metropolitan area has a population of over 32 million, making it the world’s fourth-largest metro area. Although tornadoes are infrequent in Guangzhou, the city’s moist subtropical climate is no stranger to severe weather. Many videographers captured a brief tornado that struck the metro area on June 18, 2022, popping transformers but apparently causing no major damage or serious injuries.
Jeff Masters contributed to this post.
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