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Odd Observation?? by Wolfhound
Started on: 12-13-2006 08:18 AM
Replies: 16
Last post by: Marvin McInnis on 12-13-2006 07:59 PM
Wolfhound
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Report this Post12-13-2006 08:18 AM Click Here to See the Profile for WolfhoundClick Here to visit Wolfhound's HomePageClick Here to Email WolfhoundSend a Private Message to WolfhoundDirect Link to This Post
This is The expanded NOAA radar loop for the Continental U.S.
http://www.srh.noaa.gov/ridge/Conus/full_loop.php

I had noticed something on the site, several days ago, that's interesting and something of a mystery,

I saw what had the appearance ( For descriptive purposes only) of a wave of meteors sweeping across the radar display in the afternoon. My first thought was it was jet contrails. However they were all pointed about 20 degrees south of west and aligned roughly North to South. I considered it might be a blip and it's shadow, but that couldn't be the case since they're not aligned with a radar sources.
When I saw it again day after day I realised it wasn't a unique event. Last night I figured out what it was associated with. It's the terminal line of night and day. The head of the comet shape points toward the winter suns path.
Since I notice it was related to the setting sun, maybe it would show up in the morning terminal line.
I checked this morning and it did. at 7:00 AM it is just coming into the east coast intermingled at the moment with the rain front.
A good single example (at the moment) is between the Keys and Cuba and again it is pointed toward the Sun, But this time South of East. As the morning progresses it should travel West into clear areas where it will be more visible. These are short term events and usually appear only in one frame of the loop so they flash.
What causes this? Could be solar particles hitting the atmosphere at just the right angle, Temperature differential maybe? Any ideas? what makes it show up on the radar? Is there a observable contrail?

[This message has been edited by Wolfhound (edited 12-13-2006).]

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Wichita
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Report this Post12-13-2006 08:26 AM Click Here to See the Profile for WichitaClick Here to Email WichitaSend a Private Message to WichitaDirect Link to This Post
That the powerful laser beams that are fired off from Bush's huricane making machine. Planting the seed for a wild huricane season next year.
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whadeduck
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Report this Post12-13-2006 08:32 AM Click Here to See the Profile for whadeduckClick Here to Email whadeduckSend a Private Message to whadeduckDirect Link to This Post
You didn't see anything. Just check your peephole before you answer the door from now on and listen for beeps on your house phone.

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Wolfhound
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Report this Post12-13-2006 08:33 AM Click Here to See the Profile for WolfhoundClick Here to visit Wolfhound's HomePageClick Here to Email WolfhoundSend a Private Message to WolfhoundDirect Link to This Post
I can always depend on your genius wichita.
Anyone with intellegent thoughts on the cause.
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whadeduck
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Report this Post12-13-2006 09:04 AM Click Here to See the Profile for whadeduckClick Here to Email whadeduckSend a Private Message to whadeduckDirect Link to This Post
I thought it was interesting and I'd like to know what causes that. But as far as an explanation, I got nothin'. Sorry. So I went for the joke instead.

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Wolfhound
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Report this Post12-13-2006 09:33 AM Click Here to See the Profile for WolfhoundClick Here to visit Wolfhound's HomePageClick Here to Email WolfhoundSend a Private Message to WolfhoundDirect Link to This Post
Whade ,Just responding to the bush nonsense, no offence taken.
The fact it was interesting is why I posted it.

[This message has been edited by Wolfhound (edited 12-13-2006).]

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Wichita
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Report this Post12-13-2006 09:41 AM Click Here to See the Profile for WichitaClick Here to Email WichitaSend a Private Message to WichitaDirect Link to This Post
 
quote
Originally posted by Wolfhound:

I can always depend on your genius wichita.
Anyone with intellegent thoughts on the cause.


Talk about no sense of humor. Sheez!

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Gokart Mozart
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Report this Post12-13-2006 09:44 AM Click Here to See the Profile for Gokart MozartClick Here to visit Gokart Mozart's HomePageSend a Private Message to Gokart MozartDirect Link to This Post
The radar's range is circular. If it moves in a straight line near the edge of the range it might look like a comet.
If you go http://www.srh.noaa.gov/ridge/Conus/southeast.php and loop one frame at a time, there's a 10 minute lapse per frame. No, we're not being invaded.

[This message has been edited by Gokart Mozart (edited 12-13-2006).]

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F-I-E-R-O
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Report this Post12-13-2006 09:54 AM Click Here to See the Profile for F-I-E-R-OClick Here to Email F-I-E-R-OSend a Private Message to F-I-E-R-ODirect Link to This Post
How long before the gov't shuts down this thread?

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Marvin McInnis
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Report this Post12-13-2006 10:01 AM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisDirect Link to This Post
... We interrupt this thread to address the original question ...


Interesting observation. Even though I work with weather every day (see www.FirstAlertWeather.com), I had never noticed that.

What you are seeing is artifacts of the National Weather Service (NWS) NEXRAD doppler radars "looking" for an instant directly into the rising or setting Sun. The national composite radar image that you linked to is made up of all of the NEXRAD images in the U.S. stitched together by software, which makes the phenomenon more noticeable. If you look closely at a non-looped image, you will see that the narrower "tail" of each artifact points to one of the NEXRAD sites.

Consider that the Sun (like most stars) doesn't just emit visible light, but is also a powerful broadband radio emitter. It's to be expected that some of those emissions are in the spectral range used by NEXRAD. The NEXRAD processing software includes functions to correct for well-known anomalies, but it appears that it "blinks" for a brief period as the Sun eclipses the horizon.

If you look closely, you will occasionally see other "comet-like" artifacts that don't point into the rising or setting Sun. These are artifacts of other kinds of "anomalous propagation," usually caused by phenomena like temperature inversions, etc.

I occasionally talk with NWS people in Fort Worth, where the national composite images are produced. If I can remember, I'll ask them about this phenomenon sometime.


... We now return you to the usual O/T political bickering ....

[This message has been edited by Marvin McInnis (edited 12-13-2006).]

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Wolfhound
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Report this Post12-13-2006 05:34 PM Click Here to See the Profile for WolfhoundClick Here to visit Wolfhound's HomePageClick Here to Email WolfhoundSend a Private Message to WolfhoundDirect Link to This Post
Thanks Marvin, So what it's picking up is Microwave energy from the sun it's self. Neat.
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Marvin McInnis
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Report this Post12-13-2006 05:40 PM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisDirect Link to This Post
 
quote
Originally posted by Wolfhound:

So what it's picking up is Microwave energy from the sun it's self.



Correct.

I heard a Space Weather advisory issued by the NWS this morning that said a major solar event was underway and that, among other things, much more Auroral activity (i.e. Aurora Borealis and/or Aurora Australialis) was expected for the next 3 or 4 days. There have been a number of high-energy particle and radio bursts reported. It seems reasonable that the radar phenomenon you noticed may be especially pronounced right now, too.

See the NOAA Space Environment Center web site for more information.

[This message has been edited by Marvin McInnis (edited 12-13-2006).]

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Wolfhound
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Report this Post12-13-2006 06:38 PM Click Here to See the Profile for WolfhoundClick Here to visit Wolfhound's HomePageClick Here to Email WolfhoundSend a Private Message to WolfhoundDirect Link to This Post
On a different note. the Geminid Meteor Shower peaks tonight if you have good clear weather.
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Phranc
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Report this Post12-13-2006 06:42 PM Click Here to See the Profile for PhrancClick Here to Email PhrancSend a Private Message to PhrancDirect Link to This Post
 
quote
Originally posted by Wolfhound:

On a different note. the Geminid Meteor Shower peaks tonight if you have good clear weather.


Wher in the sky and anyone see it or just certant latitudes?
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Euterpe
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Report this Post12-13-2006 06:55 PM Click Here to See the Profile for EuterpeClick Here to Email EuterpeDirect Link to This Post
 
quote
Originally posted by Marvin McInnis:

Consider that the Sun (like most stars) doesn't just emit visible light, but is also a powerful broadband radio emitter. It's to be expected that some of those emissions are in the spectral range used by NEXRAD. The NEXRAD processing software includes functions to correct for well-known anomalies, but it appears that it "blinks" for a brief period as the Sun eclipses the horizon.



are the signals in the NEXRAD-sensitive spectrum particularly directional, so that when the sun is on the horizon they get an extra-intense burst from looking at it effectively straight-on (if in fact they are looking that direction)? or is it perhaps a lensing effect?


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Wolfhound
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Report this Post12-13-2006 07:10 PM Click Here to See the Profile for WolfhoundClick Here to visit Wolfhound's HomePageClick Here to Email WolfhoundSend a Private Message to WolfhoundDirect Link to This Post
The afternoon line is visible now through west Texas, North and West, to Nevada on the set of frames. (Note post time.)
Seems to be very close to actual sunset.
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Marvin McInnis
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Report this Post12-13-2006 07:59 PM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisDirect Link to This Post
 
quote
Originally posted by Euterpe:

are the signals in the NEXRAD-sensitive spectrum particularly directional, so that when the sun is on the horizon they get an extra-intense burst from looking at it effectively straight-on (if in fact they are looking that direction)? or is it perhaps a lensing effect?



I'm not a NEXRAD expert, but I'll try to answer your question. I will necessarily oversimplify some things.

All meteorological radars, including the NEXRAD doppler radars, operate at microwave frequencies ... which means they are as directional as light. The NEXRADs do have a narrower and more steerable beam aperture than earlier-vintage radars, so they can resolve finer detail. NEXRADs can be steered up and down as well as horizontally, which allows them to generate vertical profiles of significant storms ... permitting them to see intense precipitation and turbulence at high altitudes, many minutes before it reaches the ground. Normally, NEXRAD is pointed straight at the horizon (or only slightly elevated) and rotates through a full 360 degrees every minute or so. When it's doing a lot of vertical profiling, a full sweep can take up to 3 or 4 minutes. When NEXRAD "looks" directly at a sunrise or sunset, it probably sees signal levels tens to hundreds of times stronger than normal radar return echoes.

Incidentally, Sun eclipse (and thus "sun fade") is a daily phenomenon during a large portion of the year for communications satellites in geosynchronous orbit.

[This message has been edited by Marvin McInnis (edited 12-13-2006).]

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