[obol] White-fronted Goose migration caught on RADAR???
- From: Jay Withgott <withgott@xxxxxxxxxxx>
- To: OBOL <obol@xxxxxxxxxxxxx>
- Date: Mon, 28 Apr 2014 12:55:14 -0700
I'm not sure, but it's possible that the huge Greater White-fronted Goose
flight this morning that some folks have mentioned may have been captured on
the NEXRAD system of weather radar.
Checking the data for the Portland-region radar station, I find the following
curious pattern visible in the sequential frames 10 minutes apart:
* 18:08 UTC (11:08 local time) = a very small northward pulse of
either wind or birds.
* 18:18 UTC (11:18 local time) = a big splash of moderate movement,
unusually short-lived for a weather phenomenon: diffuse, with most movement
generally NNW, but variable.
* 18:27 UTC (11:27 local time), and since then = a return back to
the very small northward pulse of either wind or birds.
In my experience of looking at radar images, I do not recall such a sudden (one
10-min. frame) pulse of movement. However, I'm also a bit hesitant to
interpret it, because for some reason all the data between 16:48 and 18:08 UTC
(9:48 - 11:08 our time) are not being displayed. The loop simply skips from
16:48 to 18:08, which is weird. (Actually, I'm halfway wondering whether the
meteorologists may have clipped this period out, if it was showing such heavy
goose flights that they thought it must be erroneous(???).)
Greg Haworth? Colby Neuman? Others who know about the workings of
meteorologists, radar, and birds? Any insight here? And how could we obtain
data for the missing time period?
... And for those of you who have no clue what I'm even talking
about, welcome to the fascinating world of radar ornithology, or "How I learned
to love weather radar now that it lets us watch bird migration!" This article
can get you started on the basics: http://ebird.org/content/ebird/news/radar/
.
For our local region, Greg Haworth runs a daily blog each spring and fall:
http://birdsoverportland.wordpress.com/author/greghaworth/ . Required reading
this time of year.
You can explore the raw images yourself by going here:
http://weather.rap.ucar.edu/radar/ .
Click on "0.5 reflectivity" to see density of objects in the atmosphere (birds
or precipitation), or click on "0.5 velocity" to see which direction those
objects are moving. Adjust the timing of the "Loop duration" and "End time" to
see an animated loop of images for your desired period within the past 12 hours.
Oregon has only 3 NEXRAD stations (Portland, Pendleton, & Medford), so
unfortunately most of the state is uncharted terrain. I would have loved some
Eugene-area radar data this morning!
As an example, set the page for a 12-hour loop viewing velocity, and then click
on the "RTX" for the Portland station on the map. The animated loop will show
moderate NNE bird migration all night, and then the disappearing colors right
around dawn show that birds are dropping out of the sky (at 12:27 - 13:24 UTC,
or 5:27 - 6:24 local time). The shaft of color in the 13:05 frame indicates
sunrise. If it's slow or crashes, try a narrower time period.
Check this page early and often during migration. If you wake up before dawn
you can look at the data and determine whether it might be a good morning to
call in sick to work. ; )
Jay Withgott
Portland
PS -- I've been working this morning out in my yard in SW Portland, hoping to
see or hear some geese. Nada. On past migration days when I've heard them in
the daytime they've been VERY high up, just specks. Perhaps today they were
even higher? Or I simply missed them?
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