AMHERST, Mass. – One month after a rash of 12 tornadoes killed a dozen people and caused millions of dollars of damage in the Dallas-Fort Worth (DFW) area, local officials and a National Weather Service (NWS) meteorologist say a new system of five networked radars there holds promise for improving warning time and reducing false alarms in future storms and tornado outbreaks.
The DFW area saw 12 tornadoes on the day after Christmas, recalls Mark Fox, warning and coordination meteorologist for the NWS at Fort Worth. He used data from the Collaborative Adaptive Sensing of the Atmosphere (CASA) radar network designed by University of Massachusetts Amherst and Colorado State University engineers and other partners to monitor the storms and help emergency managers issue warnings and direct rescue operations that day.
“CASA was showing us a lot of small-scale features that we have not been able to see at this resolution before,” says Fox. “CASA picked up the tornado just north of Midlothian really well. Analyzing it later, I found that the signature on the radar matched pretty darn close to where the damage actually occurred, at the intersection and the street level. With the old system it would have been more like a square mile. We saw that after the fact, we were so busy with the 11 other tornadoes,” he adds.
It can take two or three days per tornado to gather data, survey and document damage, he notes, so forecasters and emergency coordinators are just now evaluating the CASA network’s contribution.
“We still need to learn how to best use that high-resolution data,” Fox points out. “It’s too early to say it saved lives in these storms, but with CASA we have been able to tell emergency managers and public safety that the damage is most likely to have occurred in very specific areas, which helps them prioritize search and rescue right after the storm passes. So right now we are still in test mode. But it’s definitely proven valuable.”
The DFW area is the first in the nation to host a CASA network of five radar units, the next generation of small, near-surface, fine-scale, rapidly updating weather radar developed by researchers at the Engineering Research Center at UMass Amherst, with partners at Colorado State University, the universities of Oklahoma, Puerto Rico and Delaware, with support from the National Science Foundation.
The CASA network uses radar units the size of a microwave oven with a 36-inch dish, deployed on rooftops or cell phone towers, compared to the current generation of larger radars mounted atop 150-foot towers. CASA’s smaller, nimbler X-band radar units are most effective when networked in groups. Because they are mounted low, there is no “blind spot,” where tornadoes form close to the ground, as with the older radar generation.
Brenda Philips, CASA co-director at UMass Amherst, says, “Using CASA data, you could track the path of the tornado down streets and through neighborhoods. By analyzing these types of events, we’ll learn how to make warnings better for everyone involved in tornado warning and response, from the NWS and emergency managers to even the public’s decision to take shelter.”
Fox says he and colleagues use factors such as lead time, that is how many minutes warning they can give to let people get to shelter, to measure success, as well as accuracy in identifying actual tornadoes, which will reduce false alarms. “If we can increase lead time by even two or three minutes and reduce false alarms, then we hope that people can begin to trust the warnings more,” he explains.
After being developed and engineered by the NSF-funded university partners over the past 10 years, the CASA network at DFW has been assembled over the past three years in cooperation with the NWS, North Central Texas Council of Governments, the City of Fort Worth, the University of Texas at Arlington, the University of North Texas, the National Mesonet Program, and technology companies EWR Weather Radar, Ridgeline Instruments, Furuno Radar, and Paroscientific, Inc.
Fox says, “The project has continued to show the benefits of adding different radars to the network. With every radar that has been added, we’ve been able to see more and more information, which is a huge positive.”
He adds, “It takes experience, just like anything. The more data we see the more comfortable we are with it; we learn from every event. In October 2014, for example, we saw 100-mile-per-hour straight line winds in Arlington. We were able to issue a severe thunderstorm warning in which we were able to tell TV meteorologists and the public about tornado-strength winds, which helped warn people of the danger.”
“The CASA network has also allowed us to pick out where the most intense rain is going to fall during heavy rain events, and where urban floods might occur. Each new skill is really helpful and I expect we will get better at this,” Fox says. Several area emergency coordinators in the greater DFW area have been working together to practice with the CASA radar system.