Radar Question

[Rainband]

Whats this????



http://tinyurl.com/39z6tb

[JonathanBelles]

my guess is that it is virga. I dont really know.

[Rainband]

Thats a lot of virga, that was my first guess too. It's not on MLB or Jax Radar. When it started It was right near Crystal River. I was thinking rutt ro

[ncupsscweather]

well we know it's not virga, but i am still trying to figure it out myself. I haven't seen the radar ever do this, but if it was falling it would be something florida needs. There are serveral area's of around 75dBZ.

[Incident_MET]

It is not a meteorological return. Since it is aligned along the radial of the Ruskin radar in separate frames of your loop it is probably interference from other radars. This is not a terribly rare phenomena.

[Rainband]

Thanks for the responses guys. incident met is that the spout off Miami in your avatar??

[boca]

Rainband remember last Sunday when we had that squall line go thru the area. The Tampa radar showed a thin but intense line about 10 miles wide. On the Miami and Melbourne radar the same line looked 50 miles wider and I'm talking about the precipitation on just the intense reds that showed up. Really strange. If I were to guess the radar sees straight lime while the earth curves giving a different perspective to that same squall line.

[wjs3]

...That's correct. The radar beam "sees" in a straight line, but:

1) The beam is tilted up, so even if the earth were flat, it would be looking higher up as it gets farther away from the radar site. As you note, the curvature of the earth increases beam elevation as you get farther away from the radar too.
2) What you sometimes see in a radar image is the composite of several scans at different tilts, thus representing different slices of the atmosphere (true of composite relectivity, not base reflectivity or single scans)
3) Refraction (bending of the radar beam) by the atmosphere can also change the height. For instance, this AM, Tampa looked surrounded by precipitation. But I think that was the morning inversion "bending" the radar beam right into the ground, which showed up as echoes.

FWIW, I started a thread on radar beam height (and Wxman57 and others gave me great answers) in the "Got a Question" forum if anyone's curious.

WJS3

[Rainband]

...That's correct. The radar beam "sees" in a straight line, but:

1) The beam is tilted up, so even if the earth were flat, it would be looking higher up as it gets farther away from the radar site. As you note, the curvature of the earth increases beam elevation as you get farther away from the radar too.
2) What you sometimes see in a radar image is the composite of several scans at different tilts, thus representing different slices of the atmosphere (true of composite relectivity, not base reflectivity or single scans)
3) Refraction (bending of the radar beam) by the atmosphere can also change the height. For instance, this AM, Tampa looked surrounded by precipitation. But I think that was the morning inversion "bending" the radar beam right into the ground, which showed up as echoes.

FWIW, I started a thread on radar beam height (and Wxman57 and others gave me great answers) in the "Got a Question" forum if anyone's curious.

WJS3

Thanks I will check that out. I didn't know it was there

[Aslkahuna]

Actually, radar does not scan in a true straight line. Becuase of atmospheric refraction the beam is actually curved-generally with a radius of 3/2 Earth's radius. However, inder conditions when there are strong discontiuities in the refractive index of the atmosphere (such as temperauture or moisture inversions the beam can be refracted differently leading to anomalous propagation of the beam. This is why precision radars used in missile tracking, etc. use a refractivity profile of the atmosphere to correct for this. In addition, soace tracking radars must also cope with the refractive properties of the ionosphere which can cause position and timing errors if not corrected for. It is the very strong variability in the ionosphere that can cause problems with GPS timing and posiiton accuracy during strong Gemag as then it's impossible for the receivers to correct for the rapid changes in the transionospheric propagation of the satellite signals.

Steve

[wjs3]

Ahhh, Steve. Always setting me straight.

Yes, refraction always happens. I was just trying to simplify and you nailed me.

WJS3

[wall_cloud]

I am assuming you are referring to the big green "blob" southeast of the radar? That's simply the radar beam refraction (as Aslkahuna defined so well) producing false returns (or AP). It almost always happens at night since that is when your inversion occurs. If you look at a mosaic loop of the country that starts before sunrise and extends into the morning hours, you'll see lots of these "crop circles" disappear with time.

[Rainband]

I am assuming you are referring to the big green "blob" southeast of the radar? That's simply the radar beam refraction (as Aslkahuna defined so well) producing false returns (or AP). It almost always happens at night since that is when your inversion occurs. If you look at a mosaic loop of the country that starts before sunrise and extends into the morning hours, you'll see lots of these "crop circles" disappear with time.

actually I was talking about bright red and oranges that ooked like storms. It was only on the TPA radar. I checked the melbourne site and it wasn't there. It was along the coast and expanded inland.

[wall_cloud]

it was probably AP. especially if it had a pattern that might have resembled spokes.