I post this with the hope it will save lives. Please pay attention when storm sirens sound.
Spotters Watched Storm Build
By Carole Liston
news@joplinglobe.com The Joplin Globe Sat Jun 04, 2011, 04:48 PM CDT
JOPLIN, Mo. — It was 5:11 p.m. Sunday, May 22, when Joplin tornado sirens sounded for the first time.
Many people glanced at darkening clouds, made note of gray-green skies, perhaps even considered getting home a little sooner than otherwise planned.
But for many, there was no alarm. There was no panic. There was no sense of urgency.
Joplin, after all, is used to tornado sirens each spring.
Click here to see video shot by storm spotters.
This was business as usual for tornado season in Southwest Missouri.
But inside Jeff Piotrowski’s storm-chasing truck, it was anything but business as usual.
Piotrowski, a storm spotter from Tulsa, Okla., was tracking the May 22 storm with his wife, Kathryn.
As they drove into Joplin on Missouri Highway 171, the storm that at first appeared to be heading for northern Joplin shifted southwest. They hurried down Missouri Highway 43, down North Main Street, then swung west onto Seventh Street.
Inside the truck, storm data revealing winds of intense velocity streamed into Piotrowski’s computers from Doppler radars in Tulsa and Springfield through his connection to NEXRAD, a network of high-resolution weather radars located throughout the country and operated by the National Weather Service.
The stream of data showed a wind shear of more than 100 knots building inside the rain curtains — and climbing fast. That high wind shear doesn’t necessarily mean a tornado is forming on the ground, but it does indicate cyclonic weather in the skies.
Piotrowski grew alarmed, nervous.
When the Baron Tornado Index for the rain-wrapped storm began to accelerate rapidly, Piotrowski said his stomach tightened with fear.
That index is a computer model that helps weather spotters assess the probability of a tornado. It measures what is known as the Tornadic Vortex Signature, or TVS, a rotation algorithm detected by Doppler radar on the rear flank of a storm. It is used to detect and track possible tornadoes for purposes of warning communities to take cover. The index is measured on a scale of 0 to 10. The higher the number, the more likely a tornado is on the ground. Piotrowski watched Joplin’s BTI leap from a 4 to a 9.9 in less than two minutes.
Racing west on Seventh Street, he spotted the telltale signs of a large debris cloud forming around the “bowl” of the storm just two miles away.
One key indicator that a tornado is on the ground is the “debris cloud,” coupled with the TVS indications of high wind shear. The wind shear kept climbing rapidly above 100 knots now, moving quickly to 120 knots, then 130, then 140.
“All the parameters said something horrible is going to come into Joplin ... I knew something horrible was about to unfold right in front of me ... I couldn’t do anything about it,” Piotrowski said.
‘Get sirens going’
Piotrowski said he has been chasing storms for 35 years, and he has chased literally hundreds of tornadoes. Nothing prepared him for the explosiveness, or the intensity, of the May 22 monster. All he could think of was warning people.
He raced past Schifferdecker Avenue heading west on Seventh Street, looking for help while Kathryn attempted to get through to emergency services. Phone signals could not get through. The “bowl” of the storm had become a green-black rotating core, clearly in view, just two miles to the south and west, near Galena, Kan.
His wife kept the video camera rolling.
“I’ve got debris on the ground, I’ve got debris on the ground — right here!” Jeff can be heard hollering at one point.
Two policemen, storm spotting near Seventh Street and Black Cat Road, came into view. They were noting the deepening green tint coming from the refracted light of hail in the storm’s vortex as Piotrowski whipped up alongside their cars. He said he hoped and prayed their communications systems were intact.
“Guys!” he pointed frantically to the swirling vortex. “The tornados are trying to come down right here, the winds are on the north, and it’s coming back around — right here. Get the sirens going, get the sirens going, I’m telling you.”
The officers indicated they were indeed calling emergency services, and with that, Piotrowski made a U-turn and went back east on Seventh Street, taking a hard right on Schifferdecker, traveling south toward 20th Street — straight into the path of the coming storm.
It was about this time that the second alarm sounded. It can be heard on the video that Kathryn kept rolling.
Two weeks after the storm, there remain a lot of questions. Some scientists are wondering why so many people died, and what lessons can be extracted from the rubble. Others are wondering why so many people lived, given the power, width and length of time the tornado was on the ground.
Continued...