Five years later, Greensburg tornado has few, if any, peers
03/24/2014 10:08 AM
08/06/2014 10:29 AM
Mike Umscheid had heard plenty of stories about powerful storms and large tornadoes during his time as a meteorologist for the National Weather Service office in Dodge City.
Still, he couldn’t believe what he was seeing on radar as night fell on May 4, 2007.
When the Energy Helicity Index hits 1, it means conditions are ideal for a tornado to develop. On this evening, the EHI reading was routinely 8, 9 or 10.
Sure enough, the radar was showing indications of a tornado on the ground in Kiowa County. One of the ways tornadoes show up on radar is a “velocity signature”: winds rapidly approaching and leaving the radar location right next to each other, suggesting intense rotation.
When the combination of those wind speeds reaches the upper 100s in knots, forecasters know a powerful tornado is likely on the ground. The velocity differential for this tornado was measuring 230 knots.
“I’d never seen a 200-knot (reading) on radar,” Umscheid said.
Chasers had been following the massive tornado since it had touched down at 9 p.m. in the dying embers of daylight, and for a while it appeared it would stay in open country. But then it veered left, heading due north directly into Greensburg.
Realizing the tornado had turned, Umscheid issued what he believes is the first “tornado emergency” in Kansas history. That warning is to be used in “exceedingly rare situations,” according to the weather agency, when a severe threat to human life and catastrophic damage from a tornado is imminent or ongoing.
Although the tornado heavily damaged or destroyed 95 percent of the town, only 11 people died. Officials later credited the low death toll to a tornado warning issued 26 minutes before Greensburg was hit, and residents heeding the warning and taking shelter.
Survivors, officials and visitors are gathering in Greensburg this weekend to mark the anniversary of the tornado that devastated the town.
“You never anticipate it happening until it does,” Umscheid said. “I never even thought, 15 to 20 minutes before it hit, that it was going to hit Greensburg. It could have veered off, like 80 or 90 percent of the tornadoes do.”
A ‘deeper respect’
What would forever be known as the Greensburg tornado was on the ground for 65 minutes, grew to a width of 1 3/4 miles, had a damage path of nearly 29 miles and had winds of up to 205 miles per hour on the ground.
Umscheid was so struck by the power of the storm that he teamed with Les Lemon, a research associate with the Cooperative Institute in Mesoscale Meteorological Studies at the University of Oklahoma, to write a research paper on the outbreak that night.
Five years later, Umscheid and Lemon remain awed by the strength of the Greensburg tornado.
“Over the years, you gain a deeper respect for the capability of what the atmosphere can really do,” Umscheid said.
A year like 2011, which saw numerous large killer tornadoes – including the April 27 outbreak in the Deep South and the Joplin tornado on May 22 – “just further enhance that appreciation,” Umscheid said.
The Joplin tornado was the deadliest in decades, killing more than 150 people as it tore through the southern part of the city less than five minutes after touching down. It was eventually rated EF-5 on the Enhanced Fujita scale, meaning it had top winds of more than 200 miles an hour.
As powerful as that tornado was, however, Lemon and Umscheid say the Greensburg tornado was probably stronger.
The velocity signature for the Joplin tornado was in the upper 100s, Umscheid said.
One tornado Lemon said may well be Greensburg’s equal was the EF-5 now called the Hackleburg tornado, which was part of the April 27 outbreak in the Deep South. A weather service survey team estimated that tornado was on the ground for 132 miles, had estimated winds reaching 210 miles an hour and was as much as 1.25 miles wide. It killed 72 people and injured at least 145.
“I think I would take Greensburg and Joplin and that storm (Hackleburg), and maybe a couple of others” in a list of the strongest tornadoes on record, Lemon said. “They’re all right up there at the top.
“It would be really difficult to say which is worse than the other.”
The Trousdale tornado
For all the attention those tornadoes have gotten for their potency, however, an even more powerful tornado may well have touched down in the moments after the Greensburg tornado had ripped through town and looped around in nearly a full circle before falling apart.
What became known as the Trousdale tornado grew to nearly 2 1/4 miles wide and stayed on the ground for more than an hour on a 27-mile track. The velocity differential for the inbound and outbound winds was more than 220 knots, said Larry Ruthi, meteorologist-in-charge of the Dodge City branch, which puts it about on par with the Greensburg tornado.
But Ruthi only rated the Trousdale tornado an EF-3 – meaning it had winds estimated between 136 and 165 miles per hour – because he didn’t see trees stripped of their bark or other damage consistent with the strongest tornadoes. The Enhanced Fujita Scale uses damage to calculate a tornado’s strength, and the Trousdale tornado didn’t hit any residential areas.
If it had, “there’s no doubt in my mind it would have been an EF-5,” said Jeff Hutton, warning coordination meteorologist for the Dodge City branch of the weather service. “It was at least as strong, or stronger, than the Greensburg tornado.”