Dual Pol Radar Tornado Detection Capabilities

Radar upgrades to Dual-Polarization began in September 2011 and continue today. When this technology first appeared on the scene, I was eager to see what it was. I found the NWS Warning Decision Training Branch shortly after and downloaded the exercises and information and became accustomed with the capabilities of Dual Pol Radar.

While my initial thought was ‘this is nothing special’, later I would become more aware of what Dual Pol could and could not do. Of course being a civilian and a Non-Meteorologists [read amateur] not being privy to the technology in use by the professionals, I am still learning. However, even to this amateur I was aware after reading and viewing the material available, early tornado detection, or should I say ‘earlier’ tornado detection was not one of the major benefits. While tornado detection may be some what better than previous, it is still a long way until the professional can tell you without a doubt where a tornado will form before it touches down. That is not saying they dont have a very good idea, which is why many times a tornado warning is issued and yet no tornado touches down. They are now able to tell when a tornado is more violent than previous by detecting the debris ball signature.

To further enforce my thoughts, I found this interesting post by Jenni Laflin of the National Weather Service. She lay’s out clearly what Dual-Polarization Radar can and can not do. Give it a read for better understanding … Here’s a snip … as she mentions “The views expressed in this article are those of the author and do not necessarily represent those of the National Weather Service.”

Dual Polarization Radar in the Media
Posted on March 16, 2012

Over the last few months, there have been several news articles floating around the meteorological community that glorify dual-polarization radar as the savior of tornado warning lead time, which is a serious misconception that needs to be addressed. I haven’t read all of these articles, but it seems that the root of this claim lies in dual-pol’s capability to more clearly detect tornadic debris via correlation coefficient. Unfortunately, when tornadic debris is detected this means the tornado is already on the ground, doing enough damage to loft sizable particles which fall into the Mie or geometric scattering regimes. By the time this signal is returned to the radar, processed at the RDA, and appears in AWIPS, we’re already seconds to minutes past tornado touchdown; read: negative lead time. Sure, a debris signature can provide more confidence that a damaging tornado is present, but waiting for that confirmation before issuing an initial tornado warning is not only unreasonable, it’s extremely dangerous. A wonderful series of training modules on the proper use of dual-pol radar is freely available from WDTB, and emphasizes many times over the potential peril in waiting for a debris signature before making a warning decision. Dual-pol radar does not – and can not – increase lead time for tornadoes.

Continue Reading here – http://stormscalemodeling.org/?p=156


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