Andra has been with the National Weather Service in Norman more than 25 years. He's seen changes.
“With the old WSR-57 radar, you essentially sat in front of a console that showed a black and white image,” he said. “Going to Doppler, it was kind of like going from radio to color television. Now the change to polarimetric data in the radar will be more like going from regular color television to HD. ... I think it is a change that everyone will benefit from.”
Andra said the technology allows forecasters to look at things such as the differences of the returned energy between the vertical phase and the horizontal. That provides details about the shape of the particle they are sampling. To really use polarimetric radar data takes a combination of different pieces of information that come back from the radar, he said. Those are compared.
“Certain combinations yield or infer different types of precipitation or droplet sizes, or in some cases, non-weather echoes, such as birds or insects,” Andra said. “We look at a combination of those, and for weather we also look at the time of year, and that tells us what is out there.”
Norman has three radars in its coverage area: one at Frederick in southwest Oklahoma, one near Lake Stanley Draper in Oklahoma City and one at Vance Air Force Base's Kegelman Auxiliary Airfield near Great Salt Plains State Park. The dual-polarization operation has been used at the latter since March 2011. The other two are expected to have dual-polarization this month.
The National Weather Service's Tulsa Forecast Office has two radars in its coverage area, one near Inola and one near Fort Smith, Ark. Both are dual-polarization. The coverage area for the forecast office at Shreveport, La., includes McCurtain County in far southeastern Oklahoma. That office has one radar that is scheduled to be operating in dual-polarization by year's end.
“Having this go into operation now gives us a chance to develop some confidence with the information,” Andra said. “It's actually quite a bit more complicated to interpret than the traditional Doppler radar information that we've worked with for many years, but everyone on our staff who is going to be making a warning or forecast decision will have been trained before these systems are operational.
“And I would say our staff in Norman is a little more experienced to begin with because we were part of a research test product several years ago when this system was still being developed.
“This will put us in a good place for the upcoming winter weather season and then the following spring severe weather season.”