Author Topic: Inacurate Radar from Beal Northern Valley California on WXunderground.  (Read 2946 times)

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Offline WxSWReddingCA

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I'm noticing an innacurate represantion of precipitation from Weather Undergound Personal stations map when it is showing Beal in Northern CA. The representation from Noaa is more accurate. How can this be ?

http://radar.weather.gov/radar.php?rid=BBX&product=N0Z&overlay=11111111&loop=yes

http://www.wunderground.com/wundermap/?lat=41.46331&lon=-123.09631&zoom=8&type=hyb&units=english&rad=1&rad.num=3&rad.spd=25&rad.opa=70&rad.stm=0&wxsn=1&wxsn.mode=tw&svr=0&cams=0&sat=0&riv=0&mm=0&hur=0&fire=0&tor=0&ndfd=0&pix=0

Offline ocala

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Re: Inacurate Radar from Beal Northern Valley California on WXunderground.
« Reply #1 on: February 17, 2009, 03:24:07 PM »
Maybe I'm not sure what specifically your talking about but I see precip from  Red Bluff down to Oakland on both images.
Other then being different colors it's expanse looks to be the same.

Offline WxSWReddingCA

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Re: Inacurate Radar from Beal Northern Valley California on WXunderground.
« Reply #2 on: February 17, 2009, 03:32:15 PM »
I know its hard to see the difference, but, notice the Beal Noaa shows precip north to about 1/2 the distance between Mt shasta and Redding, where WUnder shows south of cottonwood, which is a 40 mile difference.

Offline d_l

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Re: Inacurate Radar from Beal Northern Valley California on WXunderground.
« Reply #3 on: February 17, 2009, 03:45:07 PM »
Are the Wundermaps processed to remove ground clutter which effectively removes the lower level reflection intensities of the NWS maps? The dBz values below say 10-15 might be removed?
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Offline ocala

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Re: Inacurate Radar from Beal Northern Valley California on WXunderground.
« Reply #4 on: February 17, 2009, 03:54:51 PM »
It's because the the NOAA radar is in long range mode. The  long range radar loses resolution when in the 248NM, at far distances.
Here's the same view in short range.
http://radar.weather.gov/radar.php?rid=bbx&product=N0R&overlay=11101111&loop=no
See how it matches up with the Wunderground Image.

Offline ocala

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Re: Inacurate Radar from Beal Northern Valley California on WXunderground.
« Reply #5 on: February 17, 2009, 04:01:30 PM »
Also forgot to mention that Wunderground may not have a DBZ value for smaller echos.
Example the NOAA images start  at 05,10,15 etc.
Wunderground shows a grapgh of their colors but there isn't a number attatched to them so they may start at say 10,15,20.
Edit_ Sorry I didn't see this was already mentioned above.
« Last Edit: February 17, 2009, 04:59:31 PM by ocala »

Offline WxSWReddingCA

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Re: Inacurate Radar from Beal Northern Valley California on WXunderground.
« Reply #6 on: February 17, 2009, 06:08:21 PM »
I feel sorry for those who don't realize what is happening as you will be very wet if you believe the WU version presented in the personal stations section. The long range NOAA is showing, at least with this storm, rain that is reaching the ground (not always true here)

The similarity with the short range is right on.

 

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