Flying back from Atlanta to Jackson, my Echo Flight finally received its
downloaded Nexrad data. It showed me flying right in the middle of a big
blotch of red. I look outside the window. I'm in light 40 F light drizzle
with ceilings of about 6000 above a broken 2000 layer. I turn on the
Bendix/King RDR 2000 on-board radar. It shows nothing. Nothing on the
stormscope.

Why the huge contrast between the on-board and the Nexrad return? Perhaps
the Nexrad was picking up water far above me, while the on-board was looking
ahead (I was at 5,000.)

"Wyatt Emmerich" > wrote in message
...
> Flying back from Atlanta to Jackson, my Echo Flight finally received its
> downloaded Nexrad data. It showed me flying right in the middle of a big
> blotch of red. I look outside the window. I'm in light 40 F light drizzle
> with ceilings of about 6000 above a broken 2000 layer. I turn on the
> Bendix/King RDR 2000 on-board radar. It shows nothing. Nothing on the
> stormscope.
>
> Why the huge contrast between the on-board and the Nexrad return? Perhaps
> the Nexrad was picking up water far above me, while the on-board was
looking
> ahead (I was at 5,000.)
>

Isn't Nexrad satellite based? In that case, you would be seeing the moisture
_above_.

"Tom Sixkiller" wrote:
> Isn't Nexrad satellite based?

No. It's radar based.

> In that case, you would be seeing the moisture
> _above_.

NexRad sees precipitation returns.
--
Dan
C172RG at BFM

"Dan Luke" > wrote in message
...
> "Tom Sixkiller" wrote:
> > Isn't Nexrad satellite based?
>
> No. It's radar based.

Doesn't it have satellite overlays?


> > In that case, you would be seeing the moisture
> > _above_.
>
> NexRad sees precipitation returns.

So...why is he getting the returns he is?

"Wyatt Emmerich" wrote:
> Why the huge contrast between the on-board and the Nexrad return?
> Perhaps the Nexrad was picking up water far above me, while the
> on-board was looking ahead (I was at 5,000.)

Perhaps, but I have seen persistant false weather depictions on my
WxWorks NEXRAD display a couple of times.
--
Dan
C172RG at BFM

In article >, Tom Sixkiller
> wrote:

> Isn't Nexrad satellite based? In that case, you would be seeing the moisture
> _above_.

NexRad is the current ground based system. What he is referring to is
an uplink of the images.

"Tom Sixkiller" wrote:
> > No. It's radar based.
>
> Doesn't it have satellite overlays?

What's are those?

> > > In that case, you would be seeing the moisture
> > > _above_.
> >
> > NexRad sees precipitation returns.
>
> So...why is he getting the returns he is?

He's seeing false returns or artifacts of the process that creates the
NEXRAD composite or some fault in the system he's using to receive
NEXRAD. Also, I suppose it's possible that NEXRAD was showing some very
high altitude virga that his on-board radar was pitched too low to see.
--
Dan
C172RG at BFM

I've never used in-aircraft Nexrad. But the Nexrad images displayed on the
web by the National Weather Service has two modes, Precipitation and Clear
Air. When there isn't significant precip they use Clear Air mode that is
much more sensitive and will displays colors without any precip. Don't know
if that applies to the in-aircraft version.

"Wyatt Emmerich" > wrote in message
...
> Flying back from Atlanta to Jackson, my Echo Flight finally received its
> downloaded Nexrad data. It showed me flying right in the middle of a big
> blotch of red. I look outside the window. I'm in light 40 F light drizzle
> with ceilings of about 6000 above a broken 2000 layer. I turn on the
> Bendix/King RDR 2000 on-board radar. It shows nothing. Nothing on the
> stormscope.
>
> Why the huge contrast between the on-board and the Nexrad return? Perhaps
> the Nexrad was picking up water far above me, while the on-board was
looking
> ahead (I was at 5,000.)
>
>

Most likely the answer. Check the DBZ scale, if it starts with negative
numbers the radar is in clear air mode. In precip mode it starts at 5 dbz.

"Mick Ruthven" > wrote in message
...
> I've never used in-aircraft Nexrad. But the Nexrad images displayed on the
> web by the National Weather Service has two modes, Precipitation and Clear
> Air. When there isn't significant precip they use Clear Air mode that is
> much more sensitive and will displays colors without any precip. Don't
know
> if that applies to the in-aircraft version.

"Saryon" wrote:
> >Perhaps, but I have seen persistant false weather depictions on my
> >WxWorks NEXRAD display a couple of times.
>
> Is it possible that it's something like doppler where they have a
> sensativity setting, and when it's not raining all that hard they
> crank up the sensativity which creates returns for moisture that's
> really, really fine?

In the case I described, there was no precipitation at all.
--
Dan
C172RG at BFM

Wyatt Emmerich wrote:
> Flying back from Atlanta to Jackson, my Echo Flight finally received its
> downloaded Nexrad data. It showed me flying right in the middle of a big
> blotch of red. I look outside the window. I'm in light 40 F light drizzle
> with ceilings of about 6000 above a broken 2000 layer. I turn on the
> Bendix/King RDR 2000 on-board radar. It shows nothing. Nothing on the
> stormscope.
>
> Why the huge contrast between the on-board and the Nexrad return? Perhaps
> the Nexrad was picking up water far above me, while the on-board was looking
> ahead (I was at 5,000.)

Hi Wyatt,

I see the 12/19 date on your posting and note that I was flying on 12/18 (maybe
that's when you noticed this phenomenon?) and noticed a lot of NEXRAD radar
returns (but nothing red) in western North Carolina, but no ground stations were
reporting any precipitation.

Ceilings were in the 4-6000 range. I and several others reported light rime
icing in the 6-9000 range, in the areas where the NEXRAD was showing
precipitation returns. I ultimately descended to 5000 and completed my trip at
that altitude, below the bases, and there was no precipitation at 5000 ft.

Dave
Remove SHIRT to reply directly.

On Mon, 22 Dec 2003 10:13:18 -0500, Dave Butler wrote:

> Wyatt Emmerich wrote:
>> Flying back from Atlanta to Jackson, my Echo Flight finally received its
>> downloaded Nexrad data. It showed me flying right in the middle of a big
>> blotch of red. I look outside the window. I'm in light 40 F light drizzle
>> with ceilings of about 6000 above a broken 2000 layer. I turn on the
>> Bendix/King RDR 2000 on-board radar. It shows nothing. Nothing on the
>> stormscope.
>>
>> Why the huge contrast between the on-board and the Nexrad return? Perhaps
>> the Nexrad was picking up water far above me, while the on-board was looking
>> ahead (I was at 5,000.)
>
My guess would be the EchoFlight system had an issue. A friend of mine
had that system and kept trying to get it work for 2+ years. He had a lot
of issues with accuracy. He has recently abandoned the system and has gone
to WxWorx with XM radio. That system is working much better for him.

jerry