Mike,

I have had similar issues with nexrad but not so extreme.  Did you have it on animate?  If so, how long did it show up and how “big” did it get using the scale on the screen?  What was its movement?  Did it have a “cell” (red dot) next to it?  How far were you from the area of indicated precip? 

 

Recently, I navigated, in daylight through a broken front using XM and visual around cells and found the nexrad “somewhat” accurate.  On this trip I found the “cell” (red dot) to be accurate but no precip around it….when looking out the window at the cell (I was about 5 miles away) it matched up and was about 2 miles in diameter with plenty of moisture but nothing on the screen.  I also found areas of about 3 miles in diameter on the screen with green to red but little to no clouds in that location with visual.  To me the XM is a very good tool (cell location, moisture, location of front, type of activity, movement, lightening etc…) but you’ve got to see what’s going on and have an exit plan….

I like Charlie Kohler’s and others description on the LML a few weeks ago about this subject…i.e. never try to go on top…go under and have a plan to escape etc…

 

Why don’t you email this to XM for their comments about your specific issue?….they most likely have a “default statement” but it would be interesting to hear what they say.