Tornado caught CHILL with its antenna down

GREELEY – When a swarm of tornadoes struck Northern Colorado on May 22, they couldn’t have arrived at a less opportune time for the CSU-CHILL radar facility near the Greeley-Weld Airport.

Researchers at the facility were in the process of finishing the installation of new antenna equipment when word came that a tornadic supercell thunderstorm was bearing down on Windsor.

The storm, which struck the town about noon that day, wreaked millions in damages and amazingly took only one life.

Ironically, the facility with perhaps the most advanced radar equipment in America could only stand by and watch the storm pass through the area, gathering data only as it moved away from the region to the north.

“It was frustrating in that this was probably a one-in-100-year occurrence,´ said Steven Rutledge, atmospheric professor at Colorado State University and CHILL director. “It was just the timing of it.”

$2.5 million upgrade

The addition of the new dual-offset antenna – part of a $2.5 million upgrade at the facility – will allow CHILL to peer into storm systems up to 100 miles away and detect the presence and size of hail, rain intensity, wind speed and other factors that may be harbingers of tornadoes.

Rutledge said the equipment makes it possible to see a “single large bug up to 30 miles away.”

But Rutledge notes that CHILL does not have the ability to predict whether a tornado or storm is about to form. “We can’t look into the atmosphere and say a storm is going to form; we can only see it after it forms,” he said.

Still, the upgrade marks the first time the dual-offset antenna has been installed on a weather radar anywhere in the world. The National Weather Service plans to adopt the new technology to its national network of 150 warning radar stations starting in 2009.

Rutledge said the May 22 storm system developed so quickly and moved so fast that CHILL was not able to get a fix on it until it began moving north out of the area. But data was collected as it left the region that should prove useful for storm analysis.

“We do have some very interesting data on the tornado,” he said. “We followed the storm until it dissipated north of Wellington.”

Not designed to warn

But Rutledge said CHILL was never designed to be an early-warning facility but instead a state-of-the-art research station that produces technical information that’s incorporated into National Weather Service weather stations that do issue warnings.

“Our mission is not to track weather in real time,” he said. “Our radar is not used to disseminate real-time warnings. We’re doing the cutting-edge research that will make its way into the National Weather Service domain when they upgrade to dual polarization capability.”

David Barjenbruch, a meteorologist at the Denver/Boulder National Weather Service forecast office in Boulder, said his office did not have any interaction with CHILL on May 22 because the two facilities are separately operating systems.

But Barjenbruch noted that the NWS’s radar was able to issue a tornado warning at least 30 minutes before Windsor was hit.

“Our equipment is more than capable of determining that there was a tornado indicated with that storm,” he said.

Barjenbruch said his office issued a tornado warning at 11:18 a.m. when a twister first touched down between Gilcrest and Platteville in southwest Weld County. A tornado struck the Windsor area at 11:57 a.m., according to NWS records.

Barjenbruch said advances in weather radar – especially the advent of Doppler radar in the early 1990s that shows wind rotation – have helped increase warning time for tornadoes. That kind of advance is what NWS expects to come from research facilities like CHILL, he said.

“That (dual polarization technology) is going to be the latest and greatest radar information that we’ll have with much more definition on hail and rain,” he said. “We’ll be able to have much more detail on how we can analyze these storms.”

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