Tornadoes' 'hook echo' discovered here 60 years ago
CHAMPAIGN — Since 1950, Illinois tornadoes have touched down in April more often than any other month, but only one of those was responsible for the first radar image of a "hook echo."
And it was right here in Champaign County.
Meteorologists say the April 9, 1953, event was a big step forward in the detection of tornadoes, and Tuesday marks the 60th anniversary of a historic tornado in Champaign County that led to a better understanding of storm systems everywhere.
David Kristovich, head of the Center for Atmospheric Sciences at the Illinois State Water Survey, said a prototype for a national radar network at Willard Airport and an attentive electrical engineer deserve a lot of the credit.
"There was a strong tornado that developed from an isolated thunderstorm that moved basically on a path north of the Champaign-Urbana area," Kristovich said. "One of the technicians, Don Staggs, ... was working into the evening that day maintaining the radar system. He noticed that this weird hook shape was visible in a storm moving across just to the north of the city."
Unbeknown to Skaggs at the time, that hook shape would come to be known as a "hook echo," a signature feature in radar images of tornadoes and one of the ways meteorologists today still catch powerful storm systems.
"The next day, as he talked to some people about this, some people decided ... to go out and investigate what that was," Kristovich said.
"They were able to get picture documentation, a lot of documentation of that echo."
Kristovich called it a "collaborative" effort with credit to a lot of contributors: Floyd Huff, Stan Changnon, Homer Hiser and S.G. Bigler reported on the event and its significance. Glenn Stout, head of the meteorologic subdivision, and A.M. Buswell, the chief of the water survey, supervised the process.
The F3 tornado that the radar caught ended up being pretty destructive. It moved on a path beginning in Leverett and covered about 160 miles as the storm moved toward Albany, Ind., according to a 1954 Illinois State Water Survey report.
The report cited $4 million in property damage to destroyed farmsteads, livestock and grain stores just in Illinois.
The takeaway, Kristovich said, is that it showed radar operators what to look for in a storm.
"This gave them a shape that they could look for and warn people about storms," he said. "In fact, even today, even with our very good technology, a hook echo is one of the things people look for in storms."
A hook echo indicates that dry air is being pulled into the center of the storm, that the updraft is so strong that precipitation is being blown up and to the side, and it can also indicate that the storm is rotating.
It does not always mean a tornado is imminent, but it does signify a dangerous situation.
"That tells you that it's a very strong storm," Kristovich said.
The 1953 image captured by radar at Willard Airport led to a string of research into understanding how storms evolve and how to develop models that could better predict strong storms, Kristovich said.
Before that April 9, 1953, tornado, meteorologists had an idea about what conditions might provoke a strong storm, but tornado warning systems depended on a spotter visually confirming that a tornado was developing.
"Before that, there wasn't very much opportunity to warn right before a storm hit," Kristovich said.
He added that there is "no comparison" between today's technology and that of 1953.
"We can see these things," he said. "We know what we're looking for better."