Radar Back Up - Dual Pol Install Complete! How Will It Help? Q&A

Issued 330 pm CDT Wed Mar 14th 2012 (Updated 11:25 am CDT Tue, Apr 3rd:  Install Complete!)

The Milwaukee/Sullivan WI National Weather Service Doppler Radar (KMKX) has received an important upgrade to what is known as Dual-Polarization or Dual-Pol.  The installation is now complete! 

For more information on this upgrade, please see our previous article from October 2011.

For questions and answers regarding dual polarization and the upgrade, click here (just takes you to the Q and A section at the bottom of the page).

In addition to Milwaukee/Sullivan (KMKX), Chicago IL (KLOT) and Davenport, IA (KDVN) have received the upgrade.  Other nearby radars that will receive the Dual-Pol upgrade soon include La Crosse WI (KARX) by late April 2012, and Green Bay WI (KGRB) by the middle of May 2012.


Benefits of Dual-Pol:

  • Better estimation of total precipitation amounts
  • Better estimation of the size distribution of hydrometeors (raindrops, snowflakes, hailstones, drizzle)
  • Much improved ability to identify areas of extremely heavy rainfall that are closely linked with flash floods
  • Improved detection and mitigation of non-weather related radar echoes (chaff, smoke plumes, ground clutter)
  • Easier identification of the melting layer (helpful for identifying snow levels in higher terrain)
  • Improved ability to classify precipitation type
  • Ability to identify tornado damage even before confirmation by spotters
  • Other new severe thunderstorm signatures

The full benefit of dual-pol radar, however, will not be fully realized until NWS forecasters and research meteorologists develop real-time expertise.

Thus, we do not necessarily expect to have longer lead times for tornado warnings and the like.  However, we do expect to have more detailed information about winter storms, heavy rain events, and severe storms.  More specific information about the location and magnitude of the storms will be available than ever before.

Below are some examples from the recent "Leap Year" tornado events in southern Missouri on Feb 29th 2012 (courtesy National Weather Service Springfield MO).

In the first image, there is a four panel image of an EF2 (strong) tornado that went through parts of Branson MO (center of the four images, with a small square cursor denoting location.   In the upper left, the tornado was embedded in heavy rain and its location was not obvious.  In the lower two panels, some complex new Dual-Pol algorithms indicate the location of debris lofted by the tornado, with a black "hole" in the lower left and a product in the lower right that shows a different composition of particles (greenish-blue) surrounded by rain (red and purple).  

 

 

 


The second image below is also from the same time, with Branson in the center of the four images.  The two top images are velocity images that show the tight couplet (red and green next to each other) where red is air flowing south and green moving north.  In the bottom left, the radar identifies an area of hail near Branson (though it was actually debris in this case). 

 


The 3rd image below is from another tornado that night that was just southwest of Buffalo Missouri at the time.  The upper left image shows the primary part of the severe thunderstorms from near Buffalo and extending to the south and southeast of Buffalo.  There is a small and nearly separate heavy echo a few miles to the southwest of Buffalo...which again shows a "black hole" in the lower left image and much different particle composition in the lower right image (blue-ish green surrounding by red and purple). 

 

 

 


The 4th and final image shows velocity images showing the tornado southwest of Buffalo and in the center of the screen.  In the lower left, because of the debris signature, shows either large hail or "Unknown" as the preciptiation type, since tornado debris will look very different to the Dual-Pol radar than typical raindrops or snowflakes do. 

 




Dual-Pol Questions and Answers:

Q: How much does each upgrade cost?
A: The approximate cost for upgrading each radar is $225,000 for parts and labor.


Q: How much does the program cost?
A: The approximate cost for the entire program is $50M.

 

Q: How does dual polarization technology improve flood forecasts?
A: One of the main advantages of upgrading to dual polarization technology is improved precipitation estimation. Forecasters who examine the new data are able to pinpoint areas of heavy rainfall much better than with existing radar technology, and radar‐estimated rainfall amounts will be more accurate. Armed with this new information, forecasters are able to detect flash floods much better than before and improve accuracy and lead time for flash flood warnings.


Q: How does dual polarization technology improve winter weather forecasts?
A: During winter weather events, current radar technology makes it very difficult to tell the difference between the various types of winter precipitation. Dual polarization radar provides the ability to tell the difference between rain and snow, which gives forecasters a much better
idea of what to expect on the ground. For instance, current radar technology allows forecasters the ability to detect the presence and movement of winter precipitation, but it is very difficult to infer whether it is rain, snow, or a mixture of both. Dual polarization radar data provide certainty that at the height of the radar beam the precipitation is rain, snow, or a mixture of rain and snow, which a forecaster can then infer the eventual precipitation type at the ground based on environmental conditions from the radar beam to the ground.


Q: Does dual polarization technology improve what forecasters see?
A: Yes. Normally when we look at the radar we’re looking for weather. Dual polarization radar can actually tell the difference between the weather and areas that might contain birds, bats, and insects, targets that are difficult to identify and remove automatically with existing radar technology. Dual polarization radar data can correctly identify more than 99 percent of nonweather targets, enabling the automated removal of these non‐weather targets and a much cleaner radar display, making it much easier to focus on the weather.

 

Q: Is there information explaining dual polarization technology that is brief and simple to
understand?
A: Yes, a short video produced by NOAA is available on YouTube that explains the basic benefits of dual polarization for the general public. Anyone can link to the video, which includes subtitles:

http://www.youtube.com/watch?v=tX6LH_l3P3Y

 

Q: Will dual polarization technology improve tornado warnings?
A: Dual‐polarization radar technology can detect and identify the presence of tornado debris, giving the forecaster a high degree of confidence that a damaging tornado is on the ground. This also helps a forecaster pinpoint and track the location of a tornado. This is especially
helpful at nighttime or with tornadoes that are rain‐wrapped, essentially whenever reliable spotter reports are unavailable.


Q: Will the radar upgrade help forecast tornadoes in advance?
A: While dual polarization radar provides specific information about the location of a tornado, at this point it does not provide added information about where a tornado will form ahead of time.


Q: Will dual polarization technology improve hail forecasts?
A: Dual polarization radars allow forecasters the ability to pinpoint where in the storm hail is falling. It also provides the ability to detect giant hail, roughly larger than golf balls. Over the next several years, hail size estimation will be vastly improved.

 For more frequently asked questions, click here.

 


 
Jeff Craven,  Science and Operations Officer

National Weather Service, Milwaukee/Sullivan WI



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