Low precipitation band

[Duane Tiemann]

We often see a line of generally lower precipitation during storms. See attached AccuWeather radar maps.

What could cause this? Is there a name for it?

Thanks, Duane

 

[KoD]

That is a radar artifact, something close to the radar could be blocking the beam or the return.

I found the radar and found a narrow slice of missing returns and drawing a line seems to match up with what you're seeing here.

 

[Duane Tiemann]

Thanks. That seems really credible. A few things might throw a little shade on it, though.

I neglected to mention that after a while it seems to drift off to the northeast. I don't have an image of that. Next time I see it, I'll make sure to capture it.

I've also seen it on Darksky, but much less pronounced. I assume they report from the same radar.

And it doesn't always happen. Next time I see it not happen, I can take a screen shot as well.

Wouldn't a radar blockage produce more of a wedge pattern?

Again thanks,

Duane

 

[KoD]

It is wedge shaped, you can see it much more pronounced in this gif since there's a lot more precipitation involved.

You can see there's a few other narrow bands of abnormal attenuation close to the band of no data.
I don't know if there's something physically blocking the beam or if there's a fault in the radar but there's not any atmospheric phenomenon going on that's creating those abnormal lines.

 

[Duane Tiemann]

Thanks. That helps. I'm convinced. I can imagine that the 'fact' that it moves and disappears could be that the blockage, whatever it is, moves a bit.

Duane

 

[KoD]

Sure. I did more looking into it and apparently there's a water tower to the WNW of the radar that's blocking the beam

During our visit, Meteorologist Gary Conte told us that a water tower near the radar blocks a tiny fraction of reflectivity. That fraction amplifies over a long distance, becoming significant enough to take a chunk out of the data!

I can't explain why it would be moving though lol

 

[Duane Tiemann]

I definitely remember it moved. That doesn't mean it actually moved. My memory is not the best.

 

[Duane Tiemann]

Yup. It definitely moves. But it starts moving at "now" in the AccuWeather animation. The line persists and drifts in the projected future radar map.

Duane

 

[KoD]

Yup. It definitely moves. But it starts moving at "now" in the AccuWeather animation. The line persists and drifts in the projected future radar map.

Duane

Yeah so anything after "now" is computer generated based on the radar, so it's moving that line as if it's a feature of the radar return. The algorithm they're using to project anything beyond "now" doesn't discern that region as being static. You can find this on some websites but as far as historical radar data, this line has remained there and never moved for at least 11 years.