[wisb] Re: Nexrad images from last night
- From: John Idzikowski <idzikoj@xxxxxxx>
- To: dkkearns@xxxxxxxxxxx
- Date: Sun, 16 Oct 2011 18:04:29 -0500 (CDT)
"Wonder what an 18th century radar must
have been like before the white man got here and shot everything up?"
Excellent question- Sidney Gauthreaux, our modern father of Nexrad radar and
bird migration believes that pre-settlement nocturnal peaks in spring and fall
commonly exceeded 40 dbz, especially over what is now Brownsville, Texas; dbz
is the standard measurement used to correlate density of birds (or weather) as
a function of reflectivity of the radar beam-
http://my.execpc.com/CE/5F/idzikoj/nexrad/nexweb/Slide12.JPG
-40 dbz calibrates to well over 5000 birds per cubic kilometer.
Now the peak over Brownsville reaches 35 regularly during peak times. In
Wisconsin 35 dbz is rare but 30-35 occurs at LaCrosse Nexrad once or twice a
season and usually a bit more commonly at Duluth where migrants often
concentrate avoiding passage over Lake Superior. This fall we are seeing some
of the latest heavy nights in excess of 25 dbz that I have ever seen in the 10
plus years that this imagery has been available. The slow west to east
movements of weather systems that have apparently held migrants back began with
that extraordinary "cut-off" low that stayed in place for a week in late
September.
John Idzikowski
Milwaukee
----- Original Message -----
From: "Kevin Kearns" <dkkearns@xxxxxxxxxxx>
To: "Wisconsin birding network (E-mail)" <wisbirdn@xxxxxxxxxxxxx>
Sent: Sunday, October 16, 2011 5:17:29 AM
Subject: [wisb] Nexrad images from last night
Very large number of migrants moving through the south tonight based on
radar captures from the southeast. Wonder what an 18th century radar must
have been like before the white man got here and shot everything up?
http://badbirdz2.wordpress.com/2011/10/16/do-you-see-what-we-see-go-birding/
Kevin Kearns
Lake Mills
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