Okay, this is really strange weather map(Vanity)

wunderground ^ | 3-20-08 | me

[Judith Anne]

This is the strangest weather radar map I have ever seen: green circles around St. Louis, Kansas City, Springfield, Des Moines, and a couple others--clear in the middle, green doughnut of precip all around.

Yes, I am logged in. A moose bit my sister, but it was years ago. My beeber has never been stuned.

These circles are strange. Can someone get a screen capture for the thread, please, as a favor?

[Judith Anne]

Okay, that’s a much better map. Thanks, Hal.

Whew! You just never know......

[Judith Anne]

Neat link, thanks. Eureka was all over Fox News this morning due to the amazing floods...lots down here, too, and the rivers aren’t crested, yet. My little area of living and working is fine, but a section of I-44 was going to close, if it hasn’t already, according to what I heard.

[stlnative]

Since you are in MO this site is helpful on which roads are flooded (snow covered, etc) in MO.

http://maps.modot.mo.gov/travelerinformation/TravelerInformation.aspx

[stlnative]

what is your general location in MO.?
I am on the IL side in Chester IL (sits high on the bluffs above the Mississippi)
Our crest is set for Sunday now at about 38.0+ ft (11 ft over flood stage)

[JRios1968]

I'd say you picked the wrong week to quit drinkin' coffee

[Judith Anne]

South central. There are flooded/closed roads to the south, west, north, and east. :D True.

[Judith Anne]

Don’t you think that’s a strange looking radar map at the top?

[endthematrix]

[JRios1968]

It’s just the alien invasion...oops

[Judith Anne]

My guess is that the centers are the radar sites.

So, ALL the radar sites have their gain turned up high in those cities? I'm going to check the link for all the regions, and see if there's more of this elsewhere.

[stlnative]

It looks like part of I-44 (east bound) by Arlington Outer Rd in Phelps Co is closed.

[Judith Anne]

Oh, now that is just spooky looking.

All the radars over a third of the US have their gain turned waaaaaaaay up, and even though there’s no precip, there are a boatload of circular ground clutter patterns.

I have never seen or heard of this before. I still say it could be THE alien invasion we’ve all heard so much about. Right in flyover country, too.

[ThePythonicCow]

Why are the centers empty? Looks like a doughnut.

The radar is not looking exactly horizontal. It's situated on the ground looking up at a slight angle, and the earth's surface is falling away, at a slighter angle. So you are looking at an angled cross section of the sky.

In the case say of the donut shape, this means that close to the radar, and really close to the deck, the sky was clear. A little further out, and higher up, there was enough to reflect back to the radar. Further out and higher up still, clear again.

[Judith Anne]

And all those radars are set up the same way, to make the same effect, all over the center of the country.....?

[ThePythonicCow]

And all those radars are set up the same way

Well, I suppose so, yes. Most radars sit on the ground (disregarding the non-stationary ones on aircraft and ships, of course.) And if you're running a radar on the ground to see what's in the sky around you, you kinda have to angle it up into the sky, but not too steep, or you won't see anything except what's right above you.

[Judith Anne]

Okay. I just have never seen anything like this in my four years of looking at the radar maps. A first time for everything.....

[ThePythonicCow]

Now when there are more clouds, and (as others have noted) the radar gain is turned down because it can actually see something interesting resembling cloud shapes, then you'll see more familiar weather patterns.

Apparently it's clear over that part of the country now, so the radars are all just cranking up the gain to the max to see something, which is the near clutter or air near to but on the deck ... just which others on this thread understand better than I do, but whatever, the air is apparently uniformly clear over a wide area.

[endthematrix]

Best description yet:

Clutter
Ground Clutter is the most common false echo and is usually seen in every radar image. When atmospheric conditions are such where there are low-level inversions (air temperature increasing with height instead of the typical decreasing with height) ground clutter can be very pronounced.

Ground clutter is the easiest false echo to recognize since it does not move in any organized fashion, it has no kind of structure to it that is similar to real precipitation, and it is usually close to the radar. The ground clutter in clear air mode is often more prevalent than precipitation mode. This is because the radar is in its most sensitive operation thereby “seeing” smaller objects such as dirt, dust and bugs.

[Swordmaker]

Heat Islands?

[Judith Anne]

Oh, anyway, I was referring to the gain, mentioned by HAL9000 in post 4, all being set up the same to get this effect, not necessarily the angles...