Radar Anomalies, Catch NEXRAD doing something funny? Post here. Options

[WeatherMatrix]

I'll start us out. Like the Chicago NEXRAD did last summer, the Fresno radar is detecting cars on the highway today. I assume this because

1.) The echoes are only along the highway and
2.) The echoes don't move over time.

Here are a couple of shots, and there are some movies here (right-click/Save As required for IE).

 radanom1_21_2009_1_13_02_PM.png ( 46.69K ) Number of downloads: 0


 radanom1_21_2009_1_13_18_PM.png ( 39.78K ) Number of downloads: 0


 inxr1kfata121a.gif ( 220.3K ) Number of downloads: 0


 inxv1kfata121b.gif ( 224.69K ) Number of downloads: 0

[AnthonyS]

I've never seen this one before -- very interesting.

Anthony

[SEMIweather]

Never heard of this before, just read your blog entry on this Jesse, interesting stuff!

[Removed_Member_Bl1zzard_*]

It could be picking up the water being sprayed up by cars. The highways it's present on here clearly just had heavy rain go over them. It wouldn't necessarily account for the strong returns, but it would make sense for there to be some returns.

[SEMIweather]

It could be picking up the water being sprayed up by cars. The highways it's present on here clearly just had heavy rain go over them. It wouldn't necessarily account for the strong returns, but it would make sense for there to be some returns.

Hmm...good thought Bl1zzard, definitely believable.

[AnthonyS]

It could be picking up the water being sprayed up by cars. The highways it's present on here clearly just had heavy rain go over them. It wouldn't necessarily account for the strong returns, but it would make sense for there to be some returns.

Looking at the velocity imagery reveals two items of interest: stationary and non-stationary returns along Interstate 5.

After looking at Google Earth for the better part of an hour, it seems that the areas of higher reflectivity, which correspond to the stationary returns, are associated with large elevated objects such as overpasses, silos, etc. along I-5 (looks like a beautiful stretch to drive, by the way).

The radar is likely not picking up spray along the roads because the drop sizes are too small, and too low to the ground. Coincidentally, part of this is also the reason why the cars have low reflectivity; i.e., cars are large objects, but near the ground, so the beam returns only a slight echo.

There was probably an inversion in the Fresno Valley, which caused the HNX radar to bend back to the ground and reflect the objects along the fairly isolated interstate. If you look at the imagery, the cars, overpasses, etc. are not the only things being reflected. There are houses, buildings, hills, mnts, all sorts of things. I-5 sticks out because, again, it is fairly isolated.

Anthony

[Removed_Member_Bl1zzard_*]

Looking at the velocity imagery reveals two items of interest: stationary and non-stationary returns along Interstate 5.

After looking at Google Earth for the better part of an hour, it seems that the areas of higher reflectivity, which correspond to the stationary returns, are associated with large elevated objects such as overpasses, silos, etc. along I-5 (looks like a beautiful stretch to drive, by the way).

The radar is likely not picking up spray along the roads because the drop sizes are too small, and too low to the ground. Coincidentally, part of this is also the reason why the cars have low reflectivity; i.e., cars are large objects, but near the ground, so the beam returns only a slight echo.

There was probably an inversion in the Fresno Valley, which caused the HNX radar to bend back to the ground and reflect the objects along the fairly isolated interstate. If you look at the imagery, the cars, overpasses, etc. are not the only things being reflected. There are houses, buildings, hills, mnts, all sorts of things. I-5 sticks out because, again, it is fairly isolated.

Anthony

Fair enough.

[WeatherMatrix]

There was probably an inversion in the Fresno Valley, which caused the HNX radar to bend back to the ground and reflect the objects along the fairly isolated interstate. If you look at the imagery, the cars, overpasses, etc. are not the only things being reflected. There are houses, buildings, hills, mnts, all sorts of things. I-5 sticks out because, again, it is fairly isolated.

Anthony

That's a definite, because normally NEXRAD beam would be higher than city buildings, much less cars. But why would it reflect off the interstate (or objects near it) and not the ground itself, which you often see it doing with high dBZ anomalous propagation (even at flat places like the coast)?

[WeatherMatrix]

Spikes appeared on several NEXRADS in the Plains today around 1 PM, at one point three radars were contributing spikes, see images below. Normally spikes only occur at sunrise or sunset, but other reflections or software issues can cause them to happen at any time.

Attached File(s)

 anomaly1_23_2009_1_42_49_PM.png ( 124.54K ) Number of downloads: 0
 inxrekddca123a.gif ( 187.57K ) Number of downloads: 0
 inxrekhsia123b.gif ( 268.07K ) Number of downloads: 0
 inxrekmkca123a.gif ( 193.67K ) Number of downloads: 0

 

[futureweatherman...]

Something odd happened today with TDWR tower at the Dallas/Fort Worth area. Base Velocity 3 scans over an area of light rain skyrocketed to the 100s, both towards and away from the radar site. The next scan returned normal again:

 Radar_spaz.png ( 322.64K ) Number of downloads: 0

You can clearly see the "spaz" in one area.

 Radar_spaz2.png ( 419.58K ) Number of downloads: 0

The next image appears normal.

 Radar_spaz3.png ( 309.5K ) Number of downloads: 0

Then the next frame, you see the spike again

 Spaz.png ( 466.04K ) Number of downloads: 0

And there were multiple spikes for the next few scans



This post has been edited by futureweatherman12: May 2 2009, 04:17 PM