My work assistant sent me an article about NWS radar in Romeoville, IL detecting vehicle traffic - including some possible speeders. I've heard about doppler picking up bird migration, but this is the first I've heard about picking up vehicles.
"The doppler radar typically measures the motions of rain and water droplets toward and away from the radar, just like how a police officer's radar can pick up on a car's speed. But when a low level inversion (a layer of warmer air up above the surface) develops, it can cause the beam to be re-directed toward the ground and pick up on dense objects like buildings or traffic on highways. In this instance, the radar was able to pick up on traffic across Livingston County along I-55 as well as Iroquois County along I-57. "
FLASH FLOOD WARNING TECHNOLOGY AND METRICS::
a large traffic backup as vehicles stalled in the. high waters. Water Weather Surveillance Radar, 1988 Doppler (WSR-88D) reflectivity-rainrate (ZR)
http://ams.confex.com/ams/pdfpapers/81746.pdfHOME |
http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=lot&storyid=17311&source=0
Not entirely traffic, but here is an interesting link from the SPC. It is a radar loop featuring some of the bats from Austin being sucked into the updraft of a supercell.
http://www.spc.noaa.gov/coolimg/batrad/javaloop.htm
I also remember seeing the radar out of FWD when Columbia broke apart over North Central Texas. The debris was picked up in a line heading NW to SE.
If anyone is bored at about 8:30 pm central time take a look at the central Texas Radar on Any clear night. You will see what looks like a mini supercell going up then spreading out to the north east over IH 35 in Round Rock. This is our mega Bat colony taking off from under the IH 35 overpasses. I will get a picture of the bats leaving and post it... It is like a big blackk cloud...
The first time many see this radar image they think it is a cell going up! HaHaHA!! Right Aaron?!
Cheyenne is notoriously bad as well ... you should see all the mesos and TVS' on I-80!
As David noted, it's relatively common in the southern and central Plains to see traffic returns as the nocturnal inversion sets up after peak heating. I've seen it on TLX, AMA, and LBB, to name a few, though I can understand how those not from the area (and thus those who probably don't watch the southern Plains radars on a regular basis) wouldn't see it often. :) The spectrum width tends to be very high given the number of vehicles on the roads and differences in speeds - 0 m/s for the ground interspersed with a few vehicles that may be going 25-35 m/s.
The "speeders" line was incorrect... Nobody was going 100+mph on both side of the expressway at the same time, let alone in rush hour :) Nonetheless, neat find. It does happen quite often at the radarsites across the country which have a major road along radials.
Here is the radar return of our bat colony taking off tonight. This then spreads to the east.
Not surprising. I recall that Salt Lake City was especially notorious with this, though I can't recall if the famous "traffic images" were with the older radars at a different site or with the new WSR-88D. Anyway I checked it out and lo and behold I can see traffic on the velocity products.
http://www.weathergraphics.com/tim/slc-v.jpg
Here is one I grabbed one night from the LBB radar. Traffic showing up on almost every major road that radiates from Lubbock.
http://wx5tvs.com/ST/lbb%20traffic.jpg
http://wx5tvs.com/ST/lbb%20traffic.png
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