Since the early 90’s, Americans have learned the word NEXRAD. The radars used by the National Weather Service has a real name though, WSR-88D. But since that’s not very sexy, to the public they’re known as NEXt generation RADar, or NEXRAD.
Trouble is, it’s been a full generation since their creation and installation. It seems they are a little too old to be called “next generation.” Well quietly, scientists have spent years on a substantial and meaningful upgrade. What is it called? Dual Polarization Radar, or Dual-Pol.
So what’ the difference? To answer that you have to understand how NEXRAD works. NEXRAD is a powerful doppler radar that can accurately scan further than any other radar before it. The doppler effect is used to not only scan for storms, but analyze them by scanning on multiple levels to create a three dimensional look inside a storm.
The utilization of NEXRAD has dramatically increased the ability to issue warnings before severe weather strikes. NEXRAD also allows meteorologist to look at wind velocities inside a storm in an effort to detect rotation developing tornadoes.
Much of this will not change with Dual-Pol Radar. So what’s so great about Dual-Pol? Dan Miller from the National Weather Service in Duluth, Minnesota gave us a chance to answer that ourselves. To me the answer is… it’s the little things.
NEXRAD can detect reflection rates. But that doesn’t tell meteorologists what that reflection means. Is it heavy rain, or is it hail? Is it sleet, or is it heavy snow? With incredible new algorithms researchers have devised along with multiple new scans that dual-pol is able to do, the goal is to not only tell people precip is coming, but exactly what type it is.
One other way this will become invaluable is winter weather. At time it can appear extremely heavy snow is about to fall, but instead it falls as sleet. On the flip side, sometimes the guess is sleet will fall and instead several inches of snow.
Coming away from the presentation given to us, I feel this will greatly impact the number of false warnings issues. As we focus on limiting the number of false tornado warnings, this goes a dramatic further in limiting the number of false thunderstorm warnings.
If the radar indicates a powerful storm, but the new new Dual-Pol features tell meteorologists there’s no hail, just heavy rain, the National Weather Service can avoid issuing an unneeded thunderstorm warning.
This upgrade will enter a full testing phase this winter at select sites. With so many NEXRAD radars across the country, it will take years to upgrade the entire grid. Either way, its an exciting change in radar technology not seen in nearly 20 years.