Phantom Weather Indication

[Glen Davis]

I have a G3X, GTN 750, 345r remote transponder.  The other day I was flying in clear skys with 20 mile viz.  There were some broken clouds above me but NO VISIBLE MOISTURE anywhere to be seen.  Nevertheless, the nexrad weather on the 750 and the G3X both showed light and moderate rain.  In the photo I was flying through an area of light and dark green but there was no rain on my aircraft or anywhere in sight for at least 20 miles.  This was not because of weather that was old.  It was less then 5 minutes old and these phantom reading happened for about 100 miles.  Do I have a problem with my equipment of is this a different problem.  Before I had the Garmin equipment I fly for years with a Stratus for weather and never experienced this.

 

[Pinecone]

I have seen this a few times.  I figured that there was rain from the clouds, but it was evaporating before it got down to my altitude.

[Andy95W]

Virga 

[exM20K]

Well, it could be Virga, the clouds off to your 10 or 11 o’clock don’t appear well developed enough to produce virga.  On several occasions in the past, I’ve had ATC call out significant weather ahead in a clear blue sky. I suspect that these are processing errors as the raw radar scans are amalgamated into the picture that gets distributed. I passed my meteorology – student son, or a more technical answer. Standby. 
 

ps. Nice panel, Glen. You and M still come down to Florida? 
-dan

[Greg Ellis]

@Scott Dennstaedt, PhD may be able to explain this.

[PT20J]

There are differences in how the various equipment processes the NEXRAD data. I have noticed that the Garmin displays often show heavier returns than show up on ForeFlight even though the GTX 345 is the source for all. I often see virga on the G3X map. It will show on ForeFlight also, but doesn’t appear as heavy.

[Scott Dennstaedt, PhD]

20 hours ago, Glen Davis said:

I have a G3X, GTN 750, 345r remote transponder.  The other day I was flying in clear skys with 20 mile viz.  There were some broken clouds above me but NO VISIBLE MOISTURE anywhere to be seen.  Nevertheless, the nexrad weather on the 750 and the G3X both showed light and moderate rain.  In the photo I was flying through an area of light and dark green but there was no rain on my aircraft or anywhere in sight for at least 20 miles.  This was not because of weather that was old.  It was less then 5 minutes old and these phantom reading happened for about 100 miles.  Do I have a problem with my equipment of is this a different problem.  Before I had the Garmin equipment I fly for years with a Stratus for weather and never experienced this.

 

It's hard to see from the picture exactly where and when this is.  Are you using SiriusXM or FIS-B? It could be virga if the air was fairly dry below the cloud base.  It could also be ground clutter or anomalous propagation from NEXRAD.  Need more info from you in order to help identify what might be going on.