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Noise on NEXRAD

Posted by Scott Dennstaedt 
Noise on NEXRAD
January 17, 2012 02:22PM
Sometimes you may see some interesting images when viewing the WSR-88D NEXRAD Doppler radars. Here's one that I captured the other day out of North Platte, Nebraska.

http://avwxworkshops.com/forum/file.php?8,file=117,filename=LNX-Radar-Rings.gif

There are dozens of reasons why we get strange returns and patterns on NEXRAD. In this case, this anomaly lasted just a few minutes it and was caused by a hiccup in the radar. The weather surveillance radar (located in Thedford, NE) uses a signal that bounces back to the radar from, say a storm cloud or precipitation. In order for the radar to know there is precipitation to display the signal needs to be stronger than the internal noise that this radar equipment naturally has.

At this particular time, the internal noise (something the radar operators monitor continually), was about 30,000K. Normal noise is about 300K. The radar interpreted all this internal noise as a return signal that was pretty strong and because the noise was constant, the radar displayed the return an equidistant from the antenna. Voile! Instant confusion for all. The 'noise' soon returned to it's normal level on the next scan.

In some cases, these unusual NEXRAD returns can make it through the XM weather filters and appear in the cockpit as I discuss in this workshop.

Scott Dennstaedt
CFI & former NWS meteorologist
Administrator of AvWxWorkshops.com
Most pilots are weatherwise, but some are otherwise™



Edited 2 time(s). Last edit at 01/17/2012 02:26PM by Scott Dennstaedt.
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open | download - LNX-Radar-Rings.gif (46.3 KB)