Garmin 396 Weather avoidance.. [Archive]

Bob Gardner

June 9th 06, 10:51 PM

The first thing you need to understand is that the weather you see on the
396 is several minutes old...possibly as much as eleven minutes. So you need
to watch the display and figure out which way the echoes are going, and plan
on passing them on the upwind side. Then you need to realize that radar
reflects only decent size rain droplets, not vertical currents, not the tops
of clouds, not turbulence. Bottom line is: Stay well clear of anything
green...yellow and red go without saying. If you have to get into the green,
make the incursion as short as possible.

Saw a revealing presentation at a NATCA controller's conference. They showed
a slide with several large cells being displayed, and indicated the position
of a 172 when the scenario began. The pilot told the controller that if he
could have a certain heading, he would be clear of the cell he saw on his
screen and could proceed to his destination. Unfortunately, by the time he
got to the geographical area which was nice and clear on his cockpit display
at the time he asked for the heading, the cell had moved directly into his
path with predictable results. The message to the controllers in attendance
was "What the pilot sees in the cockpit and real life are two different
things."

Bob Gardner

"Dan" > wrote in message
oups.com...
>
> For those of you with a Garmin 396, how do you avoid dangerous weather,
> avoid yellow and steer clear of the lightning strike indications? I am
> considering the purchase of one and am wondering how to use the info
> safely, but yet with the maximum utility.
>
> Dan
>

Peter R.

June 9th 06, 11:11 PM

Bob Gardner > wrote:

> Saw a revealing presentation at a NATCA controller's conference. They showed
> a slide with several large cells being displayed, and indicated the position
> of a 172 when the scenario began. The pilot told the controller that if he
> could have a certain heading, he would be clear of the cell he saw on his
> screen and could proceed to his destination. Unfortunately, by the time he
> got to the geographical area which was nice and clear on his cockpit display
> at the time he asked for the heading, the cell had moved directly into his
> path with predictable results.

Do you have an NTSB report or an approximate date of this accident? As a
pilot of an aircraft equipped with in-cockpit WSI weather, I am interesting
in reading more of the details surround it.

--
Peter

Bob Gardner

June 10th 06, 12:14 AM

No. The presentation was by the head man at the Air Safety Foundation,
though, and if you go to their web page you may be able to find it...or ask
them.

Bob Gardner

"Peter R." > wrote in message
...
> Bob Gardner > wrote:
>
>> Saw a revealing presentation at a NATCA controller's conference. They
>> showed
>> a slide with several large cells being displayed, and indicated the
>> position
>> of a 172 when the scenario began. The pilot told the controller that if
>> he
>> could have a certain heading, he would be clear of the cell he saw on his
>> screen and could proceed to his destination. Unfortunately, by the time
>> he
>> got to the geographical area which was nice and clear on his cockpit
>> display
>> at the time he asked for the heading, the cell had moved directly into
>> his
>> path with predictable results.
>
> Do you have an NTSB report or an approximate date of this accident? As a
> pilot of an aircraft equipped with in-cockpit WSI weather, I am
> interesting
> in reading more of the details surround it.
>
>
> --
> Peter

Dan

June 10th 06, 12:25 AM

Bob,

I would think some green would be OK if not convective (even yellow
perhaps if it is simply a heavy rain)

How can the lightning info be used? There are two types of weather
packages avaliable for the 396. One is more expensive, but includes
lightning.

Dan

Bob Gardner wrote:
> The first thing you need to understand is that the weather you see on the
> 396 is several minutes old...possibly as much as eleven minutes. So you need
> to watch the display and figure out which way the echoes are going, and plan
> on passing them on the upwind side. Then you need to realize that radar
> reflects only decent size rain droplets, not vertical currents, not the tops
> of clouds, not turbulence. Bottom line is: Stay well clear of anything
> green...yellow and red go without saying. If you have to get into the green,
> make the incursion as short as possible.
>
> Saw a revealing presentation at a NATCA controller's conference. They showed
> a slide with several large cells being displayed, and indicated the position
> of a 172 when the scenario began. The pilot told the controller that if he
> could have a certain heading, he would be clear of the cell he saw on his
> screen and could proceed to his destination. Unfortunately, by the time he
> got to the geographical area which was nice and clear on his cockpit display
> at the time he asked for the heading, the cell had moved directly into his
> path with predictable results. The message to the controllers in attendance
> was "What the pilot sees in the cockpit and real life are two different
> things."
>
> Bob Gardner
>
> "Dan" > wrote in message
> oups.com...
> >
> > For those of you with a Garmin 396, how do you avoid dangerous weather,
> > avoid yellow and steer clear of the lightning strike indications? I am
> > considering the purchase of one and am wondering how to use the info
> > safely, but yet with the maximum utility.
> >
> > Dan
> >

Bob Gardner

June 10th 06, 12:51 AM

This is from WSI's web page. Note the "near real-time" qualifier and
"mosaic."

Bob

"About WSI InFlight
The WSI InFlight system continuously broadcasts near real-time WSI aviation
weather information directly to the cockpit using a geo-synchronous
satellite service. Information includes current observed and forecast
conditions, as well as WSI NOWrad®, a high quality mosaic of the NEXRAD
Doppler radar system. WSI InFlight has complete, uninterrupted continental
United States signal reception at any altitude. The system features a
sophisticated 'high glance' value user interface that is easy to interpret
and thereby increases situational awareness. WSI aviation weather data is
provided on an 'always on' basis for a low cost, flat-fee subscription."

"Peter R." > wrote in message
...
> Bob Gardner > wrote:
>
>> Saw a revealing presentation at a NATCA controller's conference. They
>> showed
>> a slide with several large cells being displayed, and indicated the
>> position
>> of a 172 when the scenario began. The pilot told the controller that if
>> he
>> could have a certain heading, he would be clear of the cell he saw on his
>> screen and could proceed to his destination. Unfortunately, by the time
>> he
>> got to the geographical area which was nice and clear on his cockpit
>> display
>> at the time he asked for the heading, the cell had moved directly into
>> his
>> path with predictable results.
>
> Do you have an NTSB report or an approximate date of this accident? As a
> pilot of an aircraft equipped with in-cockpit WSI weather, I am
> interesting
> in reading more of the details surround it.
>
>
> --
> Peter

Bob Gardner

June 10th 06, 12:55 AM

I'm not a weather radar expert, although I have attended Dave Gwinn's
seminars on the subject. The presence of lightning means thunderstorm. In
fact, NWS people will not positively say "thunderstorm" until they have seen
lightning. So I would stay far, far away from lightning. One of the causes
of lightning is the imbalance of charges built up when air masses move in
opposite directions...like up and down.

Pure green with no yellow or red? Sure, thats plain precip. Maybe I was too
graphic in my earlier post.

The Air Safety Foundation has some dandy DVDs on this subject.

Bob

"Dan" > wrote in message
ups.com...
> Bob,
>
> I would think some green would be OK if not convective (even yellow
> perhaps if it is simply a heavy rain)
>
> How can the lightning info be used? There are two types of weather
> packages avaliable for the 396. One is more expensive, but includes
> lightning.
>
> Dan
>
>
>
>
>
> Bob Gardner wrote:
>> The first thing you need to understand is that the weather you see on the
>> 396 is several minutes old...possibly as much as eleven minutes. So you
>> need
>> to watch the display and figure out which way the echoes are going, and
>> plan
>> on passing them on the upwind side. Then you need to realize that radar
>> reflects only decent size rain droplets, not vertical currents, not the
>> tops
>> of clouds, not turbulence. Bottom line is: Stay well clear of anything
>> green...yellow and red go without saying. If you have to get into the
>> green,
>> make the incursion as short as possible.
>>
>> Saw a revealing presentation at a NATCA controller's conference. They
>> showed
>> a slide with several large cells being displayed, and indicated the
>> position
>> of a 172 when the scenario began. The pilot told the controller that if
>> he
>> could have a certain heading, he would be clear of the cell he saw on his
>> screen and could proceed to his destination. Unfortunately, by the time
>> he
>> got to the geographical area which was nice and clear on his cockpit
>> display
>> at the time he asked for the heading, the cell had moved directly into
>> his
>> path with predictable results. The message to the controllers in
>> attendance
>> was "What the pilot sees in the cockpit and real life are two different
>> things."
>>
>> Bob Gardner
>>
>> "Dan" > wrote in message
>> oups.com...
>> >
>> > For those of you with a Garmin 396, how do you avoid dangerous weather,
>> > avoid yellow and steer clear of the lightning strike indications? I am
>> > considering the purchase of one and am wondering how to use the info
>> > safely, but yet with the maximum utility.
>> >
>> > Dan
>> >
>

Robert M. Gary

June 10th 06, 01:04 AM

I wish I had an easy answer for you. However, wx is a non-trivial
subject. There are two ways you can make use of your 396 in wx. First,
you can fly with a CFI who is experienced in flying cross country.
Second you can start out very, very conservative and learn as you go
how the wx on your 396 affects your flight.

-Robert, CFI

Dan wrote:
> For those of you with a Garmin 396, how do you avoid dangerous weather,
> avoid yellow and steer clear of the lightning strike indications? I am
> considering the purchase of one and am wondering how to use the info
> safely, but yet with the maximum utility.
>
> Dan

Dan Luke

June 10th 06, 03:33 AM

"Robert M. Gary" wrote:

>I wish I had an easy answer for you. However, wx is a non-trivial
> subject. There are two ways you can make use of your 396 in wx. First,
> you can fly with a CFI who is experienced in flying cross country.
> Second you can start out very, very conservative and learn as you go
> how the wx on your 396 affects your flight.

Agree.

I have a lot of hours using XmWx to dodge CBs. I have found it to be a
wonderful tool, but it is definitely something you want to ease into as you
learn how the colored blobs you see on the screen translate to what you see
out the window.

--
Dan
C172RG at BFM

Doug Vetter

June 10th 06, 03:40 AM

Dan wrote:
> For those of you with a Garmin 396, how do you avoid dangerous weather,
> avoid yellow and steer clear of the lightning strike indications? I am
> considering the purchase of one and am wondering how to use the info
> safely, but yet with the maximum utility.

Dan,

I have only been in a few such situations since I bought the 396 last
year, and my experience is that you can fly through green all day long.
Yellow is okay as well provided it's not convective (forecasts, a
nearby lightning strike or cell data icon are a few ways one may
determine that). I always stay clear of red, since it's always
convective. The deep orange color can go either way -- I remember a day
of soaking rains that were displayed as yellow and orange, but there
were no thunderstorms in the area because the temperature and
atmospheric conditions simply didn't support convection on that scale.

I have also confirmed the lag in delivery and concur with the other
poster who suggested you determine the direction of movement and
circumnavigate on the upwind side of the cells only. I was flying
commercially one day, relocating an aircraft for some jump operations,
and had to wind my way through many cells.

I expedited my departure from the Danbury, CT airport as I watched one
cell about 10NM in diameter approach the airport. The outer edges of
the cell, depicted as green, reached the edge of the airport where I was
doing my runup when light rain started. But that cell was crawling --
almost stationary.

Enroute, I watched one cell literally explode and move at better than
30K. It took a mere three updates (15min) from this to go from one
pixel, or 2sq nm green (a "harmless shower") to a cell being tracked
upwards of 25K feet with lots of red in its core. As I watched it in
real time outside the window, it was clearly several (7-10) miles ahead
of its indicated location, though the diameter of the rain shaft
appeared roughly correct.

I just flew from NJ to SC and used the 396 for its true intended purpose
-- peace of mind. I could see the top-down weather picture and make
sure that the weather was not developing outside the scope of the
forecast. That is the way the 396 weather capability should be used --
not for close-in tactical avoidance. If you want to play that game, get
on-board radar and a stormscope...and even then second guess whether you
want to fly in those conditions.

A few caveats:

Keep in mind that I've seen shower activity (level 1, maybe 2) that does
NOT show up on the Garmin AT ALL. Do not expect to use the 396 to stay
dry. For whatever reason, it doesn't work that way.

Also, the 396's lightning data is derived from a network that records
cloud-to-ground strikes only. Cloud to cloud strikes are thus not shown
on the 396 -- you need a stormscope to see those.

Hope this helps. Safe flying,

-Doug

--------------------
Doug Vetter, ATP/CFI

http://www.dvatp.com
--------------------

Dan Luke

June 10th 06, 10:51 AM

"Doug Vetter" wrote:
> I always stay clear of red, since it's always convective.

Not always, but it is probably safest to assume it is.

--
Dan
C172RG at BFM

Sam Spade

June 10th 06, 02:59 PM

Third, you need to understand that delayed weather is not a tactical
weather avoidance device.

Robert M. Gary wrote:
> I wish I had an easy answer for you. However, wx is a non-trivial
> subject. There are two ways you can make use of your 396 in wx. First,
> you can fly with a CFI who is experienced in flying cross country.
> Second you can start out very, very conservative and learn as you go
> how the wx on your 396 affects your flight.
>
> -Robert, CFI
>
>
> Dan wrote:
>
>>For those of you with a Garmin 396, how do you avoid dangerous weather,
>>avoid yellow and steer clear of the lightning strike indications? I am
>>considering the purchase of one and am wondering how to use the info
>>safely, but yet with the maximum utility.
>>
>>Dan
>
>

Ronnie

June 10th 06, 06:19 PM

Bob,

Was this a center or approach control facility and more
specifically, was the weather info display primary or
NEXRAD? If NEXRAD, did they discuss the amount
of delay in the weather info on the controller's display? I'm
wondering if it is significantly shorter? I know the satellite
broadcast distribution adds some additional delay, but as I
undersrand it, NEXRAD radar systems take a few minutes
to build the composite view from several sweeps. Point is,
the controller's display may be a few minutes old as well.

Also, as you point out, the weather chances quickly and
the radar is only showing precip. Thus, it is not showing
the radid air currents of a developing storm. Until you have
experienced being sucked up into a radily developing convective
storm by flying through an area that your StrikeFinder and ATC
agreed was the best path, you don't fully appreciate how danerous
this type of weather can be.

I second your recommendation to stay well clear of this type of
weather.

Ronnie

"Bob Gardner" > wrote in message
. ..
> The first thing you need to understand is that the weather you see on the
> 396 is several minutes old...possibly as much as eleven minutes. So you
> need to watch the display and figure out which way the echoes are going,
> and plan on passing them on the upwind side. Then you need to realize that
> radar reflects only decent size rain droplets, not vertical currents, not
> the tops of clouds, not turbulence. Bottom line is: Stay well clear of
> anything green...yellow and red go without saying. If you have to get into
> the green, make the incursion as short as possible.
>
> Saw a revealing presentation at a NATCA controller's conference. They
> showed a slide with several large cells being displayed, and indicated the
> position of a 172 when the scenario began. The pilot told the controller
> that if he could have a certain heading, he would be clear of the cell he
> saw on his screen and could proceed to his destination. Unfortunately, by
> the time he got to the geographical area which was nice and clear on his
> cockpit display at the time he asked for the heading, the cell had moved
> directly into his path with predictable results. The message to the
> controllers in attendance was "What the pilot sees in the cockpit and real
> life are two different things."
>
> Bob Gardner
>
> "Dan" > wrote in message
> oups.com...
>>
>> For those of you with a Garmin 396, how do you avoid dangerous weather,
>> avoid yellow and steer clear of the lightning strike indications? I am
>> considering the purchase of one and am wondering how to use the info
>> safely, but yet with the maximum utility.
>>
>> Dan
>>
>
>

Bob Gardner

June 10th 06, 06:52 PM

Honestly don't know whether it was Center or terminal, but I suspect that it
was Center. The whole discussion was about delays. In precipitation mode,
the image is updated every 4 to 6 minutes. This link gives the NWS
explanation of NEXRAD.
http://weather.noaa.gov/radar/radinfo/radinfo.html. The WARP (Weather and
Radar Processor) system, which is the weather display at Center consoles,
suggests further delays as the radar information is processed (duh). I have
been beating the drums, writing letters to the editor, etc, to try to
eliminate the phrase "real-time weather" from articles and advertisements.
NO ONE gets real-time weather, not even the folks at the NWS radar sites.

Because the presentation was by the Air Safety Foundation, you might find
more info on their web site.

Bob

"Ronnie" > wrote in message
. com...
> Bob,
>
> Was this a center or approach control facility and more
> specifically, was the weather info display primary or
> NEXRAD? If NEXRAD, did they discuss the amount
> of delay in the weather info on the controller's display? I'm
> wondering if it is significantly shorter? I know the satellite
> broadcast distribution adds some additional delay, but as I
> undersrand it, NEXRAD radar systems take a few minutes
> to build the composite view from several sweeps. Point is,
> the controller's display may be a few minutes old as well.
>
> Also, as you point out, the weather chances quickly and
> the radar is only showing precip. Thus, it is not showing
> the radid air currents of a developing storm. Until you have
> experienced being sucked up into a radily developing convective
> storm by flying through an area that your StrikeFinder and ATC
> agreed was the best path, you don't fully appreciate how danerous
> this type of weather can be.
>
> I second your recommendation to stay well clear of this type of
> weather.
>
> Ronnie
>
>
> "Bob Gardner" > wrote in message
> . ..
>> The first thing you need to understand is that the weather you see on the
>> 396 is several minutes old...possibly as much as eleven minutes. So you
>> need to watch the display and figure out which way the echoes are going,
>> and plan on passing them on the upwind side. Then you need to realize
>> that radar reflects only decent size rain droplets, not vertical
>> currents, not the tops of clouds, not turbulence. Bottom line is: Stay
>> well clear of anything green...yellow and red go without saying. If you
>> have to get into the green, make the incursion as short as possible.
>>
>> Saw a revealing presentation at a NATCA controller's conference. They
>> showed a slide with several large cells being displayed, and indicated
>> the position of a 172 when the scenario began. The pilot told the
>> controller that if he could have a certain heading, he would be clear of
>> the cell he saw on his screen and could proceed to his destination.
>> Unfortunately, by the time he got to the geographical area which was nice
>> and clear on his cockpit display at the time he asked for the heading,
>> the cell had moved directly into his path with predictable results. The
>> message to the controllers in attendance was "What the pilot sees in the
>> cockpit and real life are two different things."
>>
>> Bob Gardner
>>
>> "Dan" > wrote in message
>> oups.com...
>>>
>>> For those of you with a Garmin 396, how do you avoid dangerous weather,
>>> avoid yellow and steer clear of the lightning strike indications? I am
>>> considering the purchase of one and am wondering how to use the info
>>> safely, but yet with the maximum utility.
>>>
>>> Dan
>>>
>>
>>
>
>

Newps

June 10th 06, 09:09 PM

I'm not aware of ATC displaying NEXRAD although I suppose it's possible.
We display real time weather in the TRACON up to six seconds old.

Ronnie wrote:

> Bob,
>
> Was this a center or approach control facility and more
> specifically, was the weather info display primary or
> NEXRAD? If NEXRAD, did they discuss the amount
> of delay in the weather info on the controller's display? I'm
> wondering if it is significantly shorter? I know the satellite
> broadcast distribution adds some additional delay, but as I
> undersrand it, NEXRAD radar systems take a few minutes
> to build the composite view from several sweeps. Point is,
> the controller's display may be a few minutes old as well.
>
> Also, as you point out, the weather chances quickly and
> the radar is only showing precip. Thus, it is not showing
> the radid air currents of a developing storm. Until you have
> experienced being sucked up into a radily developing convective
> storm by flying through an area that your StrikeFinder and ATC
> agreed was the best path, you don't fully appreciate how danerous
> this type of weather can be.
>
> I second your recommendation to stay well clear of this type of
> weather.
>
> Ronnie
>
>
> "Bob Gardner" > wrote in message
> . ..
>
>>The first thing you need to understand is that the weather you see on the
>>396 is several minutes old...possibly as much as eleven minutes. So you
>>need to watch the display and figure out which way the echoes are going,
>>and plan on passing them on the upwind side. Then you need to realize that
>>radar reflects only decent size rain droplets, not vertical currents, not
>>the tops of clouds, not turbulence. Bottom line is: Stay well clear of
>>anything green...yellow and red go without saying. If you have to get into
>>the green, make the incursion as short as possible.
>>
>>Saw a revealing presentation at a NATCA controller's conference. They
>>showed a slide with several large cells being displayed, and indicated the
>>position of a 172 when the scenario began. The pilot told the controller
>>that if he could have a certain heading, he would be clear of the cell he
>>saw on his screen and could proceed to his destination. Unfortunately, by
>>the time he got to the geographical area which was nice and clear on his
>>cockpit display at the time he asked for the heading, the cell had moved
>>directly into his path with predictable results. The message to the
>>controllers in attendance was "What the pilot sees in the cockpit and real
>>life are two different things."
>>
>>Bob Gardner
>>
>>"Dan" > wrote in message
oups.com...
>>
>>>For those of you with a Garmin 396, how do you avoid dangerous weather,
>>>avoid yellow and steer clear of the lightning strike indications? I am
>>>considering the purchase of one and am wondering how to use the info
>>>safely, but yet with the maximum utility.
>>>
>>>Dan
>>>
>>
>>
>
>

Sam Spade

June 10th 06, 09:45 PM

Bob Gardner wrote:

> Honestly don't know whether it was Center or terminal, but I suspect that it
> was Center. The whole discussion was about delays. In precipitation mode,
> the image is updated every 4 to 6 minutes. This link gives the NWS
> explanation of NEXRAD.
> http://weather.noaa.gov/radar/radinfo/radinfo.html. The WARP (Weather and
> Radar Processor) system, which is the weather display at Center consoles,
> suggests further delays as the radar information is processed (duh). I have
> been beating the drums, writing letters to the editor, etc, to try to
> eliminate the phrase "real-time weather" from articles and advertisements.
> NO ONE gets real-time weather, not even the folks at the NWS radar sites.

Only airborne weather radar provides real-time echos.

Newps

June 11th 06, 05:33 AM

> Bob Gardner wrote:
NO ONE gets real-time weather, not even
>> the folks at the NWS radar sites.

ATC gets real time weather, updated every six seconds.

akiley

June 11th 06, 05:10 PM

Dan wrote:
> For those of you with a Garmin 396, how do you avoid dangerous weather,
> avoid yellow and steer clear of the lightning strike indications? I am
> considering the purchase of one and am wondering how to use the info
> safely, but yet with the maximum utility.
>
> Dan

I've had a 396 for a year, but not that much weather flying with it. I
drive a lot and it's fun to analyze from the ground.

I think one of the big dangers as mentioned here before it getting into
a rapidly building tower cumulous which might not show up if you're in
the soup with your 396. I remember in Robert Buck's book "Weather
Flying" I think he said the worst turbulence he ever experienced was
in a cloud that hadn't produced rain yet.

My solution is to try to stay either above to see the buildups, or
below and avoid the rain shafts. But the 396 can also be used to find
areas of less cloud cover and lower tops. The echo tops have that
feature where you can scroll through the altitudes and watch where
cloud appears. Then you can just look for the holes in the regular
satellite display.

So to me the trick it so combine all these: The 396 weather features,
what image ATC is painting, the overall weather picture to determine if
the ingredients for convection are there, what you see out the window,
PIREPS and ride reports, tactical weather flying to try to keep
yourself visual as much as possible. Green or yellow may be fine on
days when you know there is little chance of buildups. But if green is
next to a steep gradient of yellow, into orange to red. Steer clear.

I think the 396 is an amazing tool. You can sit on the ground in your
airplane and it's almost like having the internet in your lap. I sat
on the ramp at Midway a few weeks ago and waited for a hole in the
weather using the 396. I practice with Elite simulator which will now
drive your 396 plugged into a serial port. I can put the satellite
antenna out the window to get real weather, download through Elite and
the internet real weather, and I can do near real time weather practice
sim flying. And you get a great automotive navigator for a few extra
bucks. ... akiley

Bob Gardner

June 11th 06, 07:51 PM

That's not what the NWS web page says, and it's not what I was told by the
local NWS folks. The whole discussion at the NATCA "Communicating for
Safety" conference had to do with the delays between real-time and WARP
experienced by Center controllers. One point made was that Radar and Weather
Processing involves (duh) processing, and six seconds was never mentioned.

Something is missing here, and I'm not sure where to look. But I have a ZSE
controller I can check with.

Bob Gardner

"Newps" > wrote in message
. ..
> I'm not aware of ATC displaying NEXRAD although I suppose it's possible.
> We display real time weather in the TRACON up to six seconds old.
>
> Ronnie wrote:
>
>> Bob,
>>
>> Was this a center or approach control facility and more
>> specifically, was the weather info display primary or
>> NEXRAD? If NEXRAD, did they discuss the amount
>> of delay in the weather info on the controller's display? I'm
>> wondering if it is significantly shorter? I know the satellite
>> broadcast distribution adds some additional delay, but as I
>> undersrand it, NEXRAD radar systems take a few minutes
>> to build the composite view from several sweeps. Point is,
>> the controller's display may be a few minutes old as well.
>>
>> Also, as you point out, the weather chances quickly and
>> the radar is only showing precip. Thus, it is not showing
>> the radid air currents of a developing storm. Until you have
>> experienced being sucked up into a radily developing convective
>> storm by flying through an area that your StrikeFinder and ATC
>> agreed was the best path, you don't fully appreciate how danerous
>> this type of weather can be.
>>
>> I second your recommendation to stay well clear of this type of
>> weather.
>>
>> Ronnie
>>
>>
>> "Bob Gardner" > wrote in message
>> . ..
>>
>>>The first thing you need to understand is that the weather you see on the
>>>396 is several minutes old...possibly as much as eleven minutes. So you
>>>need to watch the display and figure out which way the echoes are going,
>>>and plan on passing them on the upwind side. Then you need to realize
>>>that radar reflects only decent size rain droplets, not vertical
>>>currents, not the tops of clouds, not turbulence. Bottom line is: Stay
>>>well clear of anything green...yellow and red go without saying. If you
>>>have to get into the green, make the incursion as short as possible.
>>>
>>>Saw a revealing presentation at a NATCA controller's conference. They
>>>showed a slide with several large cells being displayed, and indicated
>>>the position of a 172 when the scenario began. The pilot told the
>>>controller that if he could have a certain heading, he would be clear of
>>>the cell he saw on his screen and could proceed to his destination.
>>>Unfortunately, by the time he got to the geographical area which was nice
>>>and clear on his cockpit display at the time he asked for the heading,
>>>the cell had moved directly into his path with predictable results. The
>>>message to the controllers in attendance was "What the pilot sees in the
>>>cockpit and real life are two different things."
>>>
>>>Bob Gardner
>>>
>>>"Dan" > wrote in message
oups.com...
>>>
>>>>For those of you with a Garmin 396, how do you avoid dangerous weather,
>>>>avoid yellow and steer clear of the lightning strike indications? I am
>>>>considering the purchase of one and am wondering how to use the info
>>>>safely, but yet with the maximum utility.
>>>>
>>>>Dan
>>>>
>>>
>>>
>>

Bob Gardner

June 11th 06, 07:53 PM

I'm guessing that a very small percentage of those who frequent this
newsgroup fly airplanes with onboard weather radar. OTOH, there are hundreds
if not thousands who have multifunction displays. My comments are directed
to that group.

Bob Gardner

"Sam Spade" > wrote in message
news:QbGig.178785$bm6.92301@fed1read04...
> Bob Gardner wrote:
>
>> Honestly don't know whether it was Center or terminal, but I suspect that
>> it was Center. The whole discussion was about delays. In precipitation
>> mode, the image is updated every 4 to 6 minutes. This link gives the NWS
>> explanation of NEXRAD.
>> http://weather.noaa.gov/radar/radinfo/radinfo.html. The WARP (Weather and
>> Radar Processor) system, which is the weather display at Center consoles,
>> suggests further delays as the radar information is processed (duh). I
>> have been beating the drums, writing letters to the editor, etc, to try
>> to eliminate the phrase "real-time weather" from articles and
>> advertisements. NO ONE gets real-time weather, not even the folks at the
>> NWS radar sites.
>
> Only airborne weather radar provides real-time echos.

Maule Driver

June 11th 06, 08:46 PM

I agree completely with akiley here.

To me, the 396's value is in adding more detail to what's already
available. Especially in terms of calibrating your eyeballs. If you
try to stay in the clear as much as possible and use the 396 to add
dimensions to what you see (and hear from ATC/pireps), you'll find it a
tremendous aid.

Having said that, any hard rules about flying thru purple and never
flying thru fuscia are generalizations at best. It's all about getting
the big picture, forecasts, actual, trends, and filling in the details.
Rain in non-convective conditions is completely different from
convective rain. Sometimes the value is all about being able to see
what's going on beyond that wall of clouds in front of you.

One of my early experiences flying north out of FL into Savannah - I
swear I was doing better with the 396 than the guys with onboard radar.
What I was seeing was probably less important to them than to me but
being able to see around corners enabled me to make the best fuel stop
while they seemed more dependent on ATC advice. Pretty amazing when
compared to pre-396 days.

akiley wrote:
> Dan wrote:
>
>>For those of you with a Garmin 396, how do you avoid dangerous weather,
>>avoid yellow and steer clear of the lightning strike indications? I am
>>considering the purchase of one and am wondering how to use the info
>>safely, but yet with the maximum utility.
a cloud that hadn't produced rain yet.
>
> My solution is to try to stay either above to see the buildups, or
> below and avoid the rain shafts. But the 396 can also be used to find
> areas of less cloud cover and lower tops. The echo tops have that
> feature where you can scroll through the altitudes and watch where
> cloud appears. Then you can just look for the holes in the regular
> satellite display.
>
> So to me the trick it so combine all these: The 396 weather features,
> what image ATC is painting, the overall weather picture to determine if
> the ingredients for convection are there, what you see out the window,
> PIREPS and ride reports, tactical weather flying to try to keep
> yourself visual as much as possible. Green or yellow may be fine on
> days when you know there is little chance of buildups. But if green is
> next to a steep gradient of yellow, into orange to red. Steer clear.
>
> I think the 396 is an amazing tool. You can sit on the ground in your
> airplane and it's almost like having the internet in your lap. I sat
> on the ramp at Midway a few weeks ago and waited for a hole in the
> weather using the 396. I practice with Elite simulator which will now
> drive your 396 plugged into a serial port. I can put the satellite
> antenna out the window to get real weather, download through Elite and
> the internet real weather, and I can do near real time weather practice
> sim flying. And you get a great automotive navigator for a few extra
> bucks. ... akiley
>

Roger

June 11th 06, 11:14 PM

On Sun, 11 Jun 2006 11:51:13 -0700, "Bob Gardner" >
wrote:

>That's not what the NWS web page says, and it's not what I was told by the
>local NWS folks. The whole discussion at the NATCA "Communicating for
>Safety" conference had to do with the delays between real-time and WARP
>experienced by Center controllers. One point made was that Radar and Weather
>Processing involves (duh) processing, and six seconds was never mentioned.

There was a news segment the other night on the next generation RADAR.
The researcher made the statement, that when they get it working they
will have "real time" images that are only ten to 15 seconds old
instead of the current 5 minutes.

And here I thought my weather service that said current really meant
current.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>Something is missing here, and I'm not sure where to look. But I have a ZSE
>controller I can check with.
>
>Bob Gardner
>
>"Newps" > wrote in message
. ..
>> I'm not aware of ATC displaying NEXRAD although I suppose it's possible.
>> We display real time weather in the TRACON up to six seconds old.
>>
>> Ronnie wrote:
>>
>>> Bob,
>>>
>>> Was this a center or approach control facility and more
>>> specifically, was the weather info display primary or
>>> NEXRAD? If NEXRAD, did they discuss the amount
>>> of delay in the weather info on the controller's display? I'm
>>> wondering if it is significantly shorter? I know the satellite
>>> broadcast distribution adds some additional delay, but as I
>>> undersrand it, NEXRAD radar systems take a few minutes
>>> to build the composite view from several sweeps. Point is,
>>> the controller's display may be a few minutes old as well.
>>>
>>> Also, as you point out, the weather chances quickly and
>>> the radar is only showing precip. Thus, it is not showing
>>> the radid air currents of a developing storm. Until you have
>>> experienced being sucked up into a radily developing convective
>>> storm by flying through an area that your StrikeFinder and ATC
>>> agreed was the best path, you don't fully appreciate how danerous
>>> this type of weather can be.
>>>
>>> I second your recommendation to stay well clear of this type of
>>> weather.
>>>
>>> Ronnie
>>>
>>>
>>> "Bob Gardner" > wrote in message
>>> . ..
>>>
>>>>The first thing you need to understand is that the weather you see on the
>>>>396 is several minutes old...possibly as much as eleven minutes. So you
>>>>need to watch the display and figure out which way the echoes are going,
>>>>and plan on passing them on the upwind side. Then you need to realize
>>>>that radar reflects only decent size rain droplets, not vertical
>>>>currents, not the tops of clouds, not turbulence. Bottom line is: Stay
>>>>well clear of anything green...yellow and red go without saying. If you
>>>>have to get into the green, make the incursion as short as possible.
>>>>
>>>>Saw a revealing presentation at a NATCA controller's conference. They
>>>>showed a slide with several large cells being displayed, and indicated
>>>>the position of a 172 when the scenario began. The pilot told the
>>>>controller that if he could have a certain heading, he would be clear of
>>>>the cell he saw on his screen and could proceed to his destination.
>>>>Unfortunately, by the time he got to the geographical area which was nice
>>>>and clear on his cockpit display at the time he asked for the heading,
>>>>the cell had moved directly into his path with predictable results. The
>>>>message to the controllers in attendance was "What the pilot sees in the
>>>>cockpit and real life are two different things."
>>>>
>>>>Bob Gardner
>>>>
>>>>"Dan" > wrote in message
oups.com...
>>>>
>>>>>For those of you with a Garmin 396, how do you avoid dangerous weather,
>>>>>avoid yellow and steer clear of the lightning strike indications? I am
>>>>>considering the purchase of one and am wondering how to use the info
>>>>>safely, but yet with the maximum utility.
>>>>>
>>>>>Dan
>>>>>
>>>>
>>>>
>>>

Sam Spade

June 12th 06, 12:21 AM

Bob Gardner wrote:
> I'm guessing that a very small percentage of those who frequent this
> newsgroup fly airplanes with onboard weather radar. OTOH, there are hundreds
> if not thousands who have multifunction displays. My comments are directed
> to that group.

Whatever. That doesn't change the fact that only airbrorne weather
radar displays real-time echos.

Newps

June 12th 06, 01:22 AM

Bob Gardner wrote:
> That's not what the NWS web page says, and it's not what I was told by the
> local NWS folks. The whole discussion at the NATCA "Communicating for
> Safety" conference had to do with the delays between real-time and WARP
> experienced by Center controllers. One point made was that Radar and Weather
> Processing involves (duh) processing, and six seconds was never mentioned.
>
> Something is missing here, and I'm not sure where to look. But I have a ZSE
> controller I can check with.

That's the center. Their display is a mosaic of many radar sites. Ask
your center buddy how often center weather radar gets updated. However
when you are talking to an approach or tower controller with radar, that
updates every six seconds. There's no processing. What I see is what's
there.

Sam Spade

June 12th 06, 02:21 AM

Newps wrote:
>
>
> Bob Gardner wrote:
>
>> That's not what the NWS web page says, and it's not what I was told by
>> the local NWS folks. The whole discussion at the NATCA "Communicating
>> for Safety" conference had to do with the delays between real-time and
>> WARP experienced by Center controllers. One point made was that Radar
>> and Weather Processing involves (duh) processing, and six seconds was
>> never mentioned.
>>
>> Something is missing here, and I'm not sure where to look. But I have
>> a ZSE controller I can check with.
>
>
> That's the center. Their display is a mosaic of many radar sites. Ask
> your center buddy how often center weather radar gets updated. However
> when you are talking to an approach or tower controller with radar, that
> updates every six seconds. There's no processing. What I see is what's
> there.

What about a TRACON with STARS?

Bob Gardner

June 12th 06, 02:24 AM

http://www.faa.gov/aua/weather/warp/

Read the first paragraph.

Bob

"Newps" > wrote in message
. ..
> I'm not aware of ATC displaying NEXRAD although I suppose it's possible.
> We display real time weather in the TRACON up to six seconds old.
>
> Ronnie wrote:
>
>> Bob,
>>
>> Was this a center or approach control facility and more
>> specifically, was the weather info display primary or
>> NEXRAD? If NEXRAD, did they discuss the amount
>> of delay in the weather info on the controller's display? I'm
>> wondering if it is significantly shorter? I know the satellite
>> broadcast distribution adds some additional delay, but as I
>> undersrand it, NEXRAD radar systems take a few minutes
>> to build the composite view from several sweeps. Point is,
>> the controller's display may be a few minutes old as well.
>>
>> Also, as you point out, the weather chances quickly and
>> the radar is only showing precip. Thus, it is not showing
>> the radid air currents of a developing storm. Until you have
>> experienced being sucked up into a radily developing convective
>> storm by flying through an area that your StrikeFinder and ATC
>> agreed was the best path, you don't fully appreciate how danerous
>> this type of weather can be.
>>
>> I second your recommendation to stay well clear of this type of
>> weather.
>>
>> Ronnie
>>
>>
>> "Bob Gardner" > wrote in message
>> . ..
>>
>>>The first thing you need to understand is that the weather you see on the
>>>396 is several minutes old...possibly as much as eleven minutes. So you
>>>need to watch the display and figure out which way the echoes are going,
>>>and plan on passing them on the upwind side. Then you need to realize
>>>that radar reflects only decent size rain droplets, not vertical
>>>currents, not the tops of clouds, not turbulence. Bottom line is: Stay
>>>well clear of anything green...yellow and red go without saying. If you
>>>have to get into the green, make the incursion as short as possible.
>>>
>>>Saw a revealing presentation at a NATCA controller's conference. They
>>>showed a slide with several large cells being displayed, and indicated
>>>the position of a 172 when the scenario began. The pilot told the
>>>controller that if he could have a certain heading, he would be clear of
>>>the cell he saw on his screen and could proceed to his destination.
>>>Unfortunately, by the time he got to the geographical area which was nice
>>>and clear on his cockpit display at the time he asked for the heading,
>>>the cell had moved directly into his path with predictable results. The
>>>message to the controllers in attendance was "What the pilot sees in the
>>>cockpit and real life are two different things."
>>>
>>>Bob Gardner
>>>
>>>"Dan" > wrote in message
oups.com...
>>>
>>>>For those of you with a Garmin 396, how do you avoid dangerous weather,
>>>>avoid yellow and steer clear of the lightning strike indications? I am
>>>>considering the purchase of one and am wondering how to use the info
>>>>safely, but yet with the maximum utility.
>>>>
>>>>Dan
>>>>
>>>
>>>
>>

Bob Gardner

June 12th 06, 02:29 AM

OK. Apples and oranges. Way back at the beginning of this thread we were
talking about using an [airborne] 396 weather display. The information sent
to cockpits, installed or handheld, is NEXRAD-based, and I jumped in to
emphasize the point that real-time weather does not exist in the cockpit
unless you have airborne weather radar, which few have. Now, all of a
sudden, you chime in with what you see at a terminal facility? Without
disclosing the kind of facility you work at?

For those late to the discussion, look at this:

http://www.faa.gov/aua/weather/warp/

Bob Gardner

"Newps" > wrote in message
. ..
>
>
> Bob Gardner wrote:
>> That's not what the NWS web page says, and it's not what I was told by
>> the local NWS folks. The whole discussion at the NATCA "Communicating for
>> Safety" conference had to do with the delays between real-time and WARP
>> experienced by Center controllers. One point made was that Radar and
>> Weather Processing involves (duh) processing, and six seconds was never
>> mentioned.
>>
>> Something is missing here, and I'm not sure where to look. But I have a
>> ZSE controller I can check with.
>
> That's the center. Their display is a mosaic of many radar sites. Ask
> your center buddy how often center weather radar gets updated. However
> when you are talking to an approach or tower controller with radar, that
> updates every six seconds. There's no processing. What I see is what's
> there.

Roger

June 12th 06, 07:47 AM

On Sun, 11 Jun 2006 18:24:20 -0700, "Bob Gardner" >
wrote:

>http://www.faa.gov/aua/weather/warp/
>
>Read the first paragraph.

Which if I understand right is about 5 minutes old by the time the
images are processed. This is the same "real time" stuff I get in my
subscription service. "Real Time" in this context meaning as soon as
they get it processed.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>Bob
>
>"Newps" > wrote in message
. ..
>> I'm not aware of ATC displaying NEXRAD although I suppose it's possible.
>> We display real time weather in the TRACON up to six seconds old.
>>
>> Ronnie wrote:
>>
>>> Bob,
>>>
>>> Was this a center or approach control facility and more
>>> specifically, was the weather info display primary or
>>> NEXRAD? If NEXRAD, did they discuss the amount
>>> of delay in the weather info on the controller's display? I'm
>>> wondering if it is significantly shorter? I know the satellite
>>> broadcast distribution adds some additional delay, but as I
>>> undersrand it, NEXRAD radar systems take a few minutes
>>> to build the composite view from several sweeps. Point is,
>>> the controller's display may be a few minutes old as well.
>>>
>>> Also, as you point out, the weather chances quickly and
>>> the radar is only showing precip. Thus, it is not showing
>>> the radid air currents of a developing storm. Until you have
>>> experienced being sucked up into a radily developing convective
>>> storm by flying through an area that your StrikeFinder and ATC
>>> agreed was the best path, you don't fully appreciate how danerous
>>> this type of weather can be.
>>>
>>> I second your recommendation to stay well clear of this type of
>>> weather.
>>>
>>> Ronnie
>>>
>>>
>>> "Bob Gardner" > wrote in message
>>> . ..
>>>
>>>>The first thing you need to understand is that the weather you see on the
>>>>396 is several minutes old...possibly as much as eleven minutes. So you
>>>>need to watch the display and figure out which way the echoes are going,
>>>>and plan on passing them on the upwind side. Then you need to realize
>>>>that radar reflects only decent size rain droplets, not vertical
>>>>currents, not the tops of clouds, not turbulence. Bottom line is: Stay
>>>>well clear of anything green...yellow and red go without saying. If you
>>>>have to get into the green, make the incursion as short as possible.
>>>>
>>>>Saw a revealing presentation at a NATCA controller's conference. They
>>>>showed a slide with several large cells being displayed, and indicated
>>>>the position of a 172 when the scenario began. The pilot told the
>>>>controller that if he could have a certain heading, he would be clear of
>>>>the cell he saw on his screen and could proceed to his destination.
>>>>Unfortunately, by the time he got to the geographical area which was nice
>>>>and clear on his cockpit display at the time he asked for the heading,
>>>>the cell had moved directly into his path with predictable results. The
>>>>message to the controllers in attendance was "What the pilot sees in the
>>>>cockpit and real life are two different things."
>>>>
>>>>Bob Gardner
>>>>
>>>>"Dan" > wrote in message
oups.com...
>>>>
>>>>>For those of you with a Garmin 396, how do you avoid dangerous weather,
>>>>>avoid yellow and steer clear of the lightning strike indications? I am
>>>>>considering the purchase of one and am wondering how to use the info
>>>>>safely, but yet with the maximum utility.
>>>>>
>>>>>Dan
>>>>>
>>>>
>>>>
>>>

Roger

June 12th 06, 08:18 AM

On 9 Jun 2006 17:04:28 -0700, "Robert M. Gary" >
wrote:

>I wish I had an easy answer for you. However, wx is a non-trivial
>subject. There are two ways you can make use of your 396 in wx. First,
>you can fly with a CFI who is experienced in flying cross country.
>Second you can start out very, very conservative and learn as you go
>how the wx on your 396 affects your flight.
>
My take on this and I've been storm chasing longer than we've had
Loran, let alone down linked RADAR. I've seen 5 tornados and one
really big water spout. I even managed to get caught outdoors along
with two of my neighbors, in a little F-1 and that can certainly raise
your sense of awareness.

The 396 has some advantages and disadvantages when compared to
airborne RADAR. Starting with the good, it does not have the blind
spots you will find from time to time in airborne RADAR caused by
absorption in heavy precipitation which can hide some nasty stuff.
OTOH if you keep in mind that the display is probably 5 minutes old or
a tad more AND you have been following it you can pick your course.

However I agree with Robert. Take a conservative approach and learn to
interpret what you are seeing on the display, how to track, and how to
predict. Learn to follow both cell and frontal movement. They are
rarely the same. Usually the cells are traveling at right angles to
the front, but NOT ALWAYS. Learn to identify upper level winds by the
rain blown off creating plumes that may or may not go in the direction
of the front or cells. You normally want to stay away from those
plumes as they may contain hail and that can be as much as 5 to 10
miles ahead of the storm at altitude. Speaking of hail and altitude,
you really don't want to run into hail in front of a cell at altitude.
It is a *lot* larger than what we see at ground level.

BTW when on the ground and in front of an approaching storm. If the
wind is blowing toward the storm that is "inflow" and a sign of a
storm with very strong convective activity.

Once you learn to determine cell movement, remember that cells can
"pop up" behind the ones you are watching. Has the storm shown a
tendency for cells to pop up along, ahead of, or behind the front. Are
the cells associated with frontal movement or a general wide spread
instability?

Knowing the storm and front movement, speed and direction along with
the knowledge the information you are seeing is at least 5 minutes old
would certainly tell me I would want to give a lot of space when
flying in front of the front or cells. OTOH Cells growing up along a
line may start to pop up on the "up wind" side of current activity.
Some times the growth of this line can be a real surprise and it can
contain some really nasty stuff.

As was said earlier. Get all the information available about the
activity and area through which you will be flying. Then use that
information along with what the RADAR is showing. A storm scope can
be really helpful in extending your "real time" knowledge of what is
going on and should be a good indicator of where those RADAR images
are headed as well as what to expect from them.

Just remember that conservative approach.

>-Robert, CFI
>
>
>Dan wrote:
>> For those of you with a Garmin 396, how do you avoid dangerous weather,
>> avoid yellow and steer clear of the lightning strike indications? I am

Yellow and even red may not indicate anything other than heavy rain if
it's not associated with convective activity. You learn what you are
seeing, where it is compared to the display, and where it is going.
Then stay out of its way. All this takes practice and liberal use of
FSS can help.

Good Luck,

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

>> considering the purchase of one and am wondering how to use the info
>> safely, but yet with the maximum utility.
>>
>> Dan

Sam Spade

June 12th 06, 02:06 PM

Bob Gardner wrote:
> OK. Apples and oranges. Way back at the beginning of this thread we were
> talking about using an [airborne] 396 weather display. The information sent
> to cockpits, installed or handheld, is NEXRAD-based, and I jumped in to
> emphasize the point that real-time weather does not exist in the cockpit
> unless you have airborne weather radar, which few have. Now, all of a
> sudden, you chime in with what you see at a terminal facility? Without
> disclosing the kind of facility you work at?
\

My recollection is that he has told the group more than once that he
works at Billings TRACON.

Sam Spade

June 12th 06, 02:16 PM

Roger wrote:

> On 9 Jun 2006 17:04:28 -0700, "Robert M. Gary" >
> wrote:

>
> The 396 has some advantages and disadvantages when compared to
> airborne RADAR. Starting with the good, it does not have the blind
> spots you will find from time to time in airborne RADAR caused by
> absorption in heavy precipitation which can hide some nasty stuff.
> OTOH if you keep in mind that the display is probably 5 minutes old or
> a tad more AND you have been following it you can pick your course.

All systems have their limitations, including airborne weather radar.
That is the reason that the prudent operation of airborne weather radar
requires minimim avoidance distances, depending upon altitude and
weather the outside air temp is above freezing.

The limitation you cite indeed exists but can be avoided through use of
distance-to-avoid parameters and not pushing the envelope to get the
mission accomplished, so to speak. The EAL wind shear crash at JFK, the
Delta L-1011 wind shear crash at DFW, and the Soutern Airways DC-9 crash
in southern Georgia all happaned when penetration rather than avoidance
was attempted..

The ideal setup in high-end aircraft today is airborne radar with the
largest feasible antenna and piped in weather radar for planning
purposes. The latter doesn't work in much of the world, though, just
like the 396 won't provide weather outside the 48 states.

Dave Butler

June 12th 06, 02:24 PM

Sam Spade

June 12th 06, 03:02 PM

Dave Butler wrote:

>
> The 396 I think still comes with the automobile kit, so on a day with
> some active weather you can stick the 396 in your car and drive around
> looking for interesting conditions. Its' a lot cheaper and safer to
> experiment in your car.

Sure does. The 396 is basically a 296 with weather option. It does
planes, cars, and boats.

Jon Woellhaf

June 12th 06, 04:27 PM

Several posters have stated that NEXRAD images displayed on the Garmin 396
are five or more minutes old because that's how long it takes for the images
to be processed before they're sent to the XM satellite.

What kind of processing could possibly take five minutes? I suspect
whomever's in control of the processing is introducing the delay so they can
sell seconds old data as a premium service.

Jon

Sam Spade

June 12th 06, 04:41 PM

Jon Woellhaf wrote:

> Several posters have stated that NEXRAD images displayed on the Garmin 396
> are five or more minutes old because that's how long it takes for the images
> to be processed before they're sent to the XM satellite.
>
> What kind of processing could possibly take five minutes? I suspect
> whomever's in control of the processing is introducing the delay so they can
> sell seconds old data as a premium service.
>
As far as I can figure out, the Nexrad updates on the www.nws.noaa.gov
occur every few minutes.

Wouldn't it require a whole lot more bandwidth to see a Nexrad site near
real time?

Bob Gardner

June 12th 06, 05:13 PM

Guess I should have remembered that. But then he should not have inserted
his comments about what he sees at a terminal facility into a discussion of
delays in cockpit weather/WARP. His radar doesn't feed NOAAPORT, so his " I
get updated every six seconds" is irrelevant.

Bob

"Sam Spade" > wrote in message
news:QFdjg.178854$bm6.100188@fed1read04...
> Bob Gardner wrote:
>> OK. Apples and oranges. Way back at the beginning of this thread we were
>> talking about using an [airborne] 396 weather display. The information
>> sent to cockpits, installed or handheld, is NEXRAD-based, and I jumped in
>> to emphasize the point that real-time weather does not exist in the
>> cockpit unless you have airborne weather radar, which few have. Now, all
>> of a sudden, you chime in with what you see at a terminal facility?
>> Without disclosing the kind of facility you work at?
> \
>
> My recollection is that he has told the group more than once that he works
> at Billings TRACON.

Bob Gardner

June 12th 06, 05:17 PM

The NEXRAD site, in order to deliver composite reflectivity, must complete a
full scan. That is, one rotation at each elevation of the transmitted beam.
That's what takes the time. Why the WARP system is further delayed is pretty
much a function of collecting scans from all of the relevant NEXRAD sites
and combining them into a mosaic, and I have no idea how much time that
takes.

Bob

"Jon Woellhaf" > wrote in message
. ..
> Several posters have stated that NEXRAD images displayed on the Garmin 396
> are five or more minutes old because that's how long it takes for the
> images to be processed before they're sent to the XM satellite.
>
> What kind of processing could possibly take five minutes? I suspect
> whomever's in control of the processing is introducing the delay so they
> can sell seconds old data as a premium service.
>
> Jon
>

Peter R.

June 12th 06, 09:18 PM

Bob Gardner > wrote:

> This is from WSI's web page. Note the "near real-time" qualifier and
> "mosaic."

Thanks, Bob. I am aware of the limitations of this and any downlinked
RADAR mosaic. In addition to Flight Service/Flight Watch, ATC weather
radar (where applicable), and eyeballs, I do use WSI for tactical (big
picture) weather avoidance. It is because of this that I was interested in
reading of the details of this particular accident.

There seem to be some vague details in the explanation of this accident
that I would like to explore. The fact that the accident aircraft was a
C172 (TAS 125 knots) and that it flew into an area of previously
convection-free activity suggests that the downlinked RADAR data were very
stale.

I certainly don't have the experience you have, but I have seen areas go
from no precipitation to level 5 precipitation in about 15-20 minutes. Is
it possible for a strong thunderstorm cell to mature quicker than that?

WSI advertises (at least when I first bought the receiver) that the radar
download would never be more than 4 minutes old. However, add to that the
"pre-processing" that they apply to the data and perhaps the picture is up
to ten minutes old.

With my WSI install, I have experienced numerous downlink outages (which
were attributable to both WSI system outages and installation problems at
my end) and significant delays in the data of up to 25 minutes, so I
learned long ago that this tool could never be used as a replacement to
active, on-board radar for navigating through a convective line.

It is worth mentioning that when the system was working and refreshing once
every four minutes, I did find the precipitation levels seem to match that
through which I was currently flying or that which I could see in the
distance.

--
Peter

Roger

June 13th 06, 08:51 AM

On Mon, 12 Jun 2006 09:27:06 -0600, "Jon Woellhaf"
> wrote:

>Several posters have stated that NEXRAD images displayed on the Garmin 396
>are five or more minutes old because that's how long it takes for the images
>to be processed before they're sent to the XM satellite.
>
>What kind of processing could possibly take five minutes? I suspect

Bob said it better than I, but it takes multiple scans, the
application of a number of algorithms, and then combining.

For an explanation as to how NEXTRAD works try
http://www.desktopdoppler.com/help/nws-nexrad.htm

We have to be careful when we refer to real time as with NEXRAD real
time does not exist. When we see the words "real time" as applied to
NEXRAD "I believe" they are referring to the time when the processing
is completed to the time you receive the image. On my systems I see
updates every 5 to 6 minutes during severe weather. Given that the
RADAR composite image takes 5 to 6 minutes to compose and it's updated
as soon as the image is completed on the commercial, subscription
sites what you know is the information is going to be older than 5
minutes. However the time from the first scan until you see the newest
image is going to be 5 to 6 minutes minimum. IOW the storm can change
substantially while the RADAR image is being generated.

There is such a thing as real time RADAR, but it's not NEXTRAD.
NEXTRAD is a very complex *system* that includes more than a simple
reflection. It includes radial winds, Rainfall accumulation, and about
5 to 10 other parameters including several modes of which I'd have to
go to the site to read.

You also have to remember that what NEXTRAD shows close in to the
station is not the same as it shows farther out. Close in images
extend from near ground level up to some specific height/altitude. 50
miles out those images start around 3000 AGL and may extend up almost
twice as high as the ones close in. Near the outer edges of the
coverage area the images may only extend down to about 5000 AGL.

NEXTRAD images composed from *Doppler* RADAR need to be processed to
find speed, intensity, and direction at each of the various levels and
then those images combined. It is much more than simply combining the
reflected signals at the various levels. Currently I believe for
complete processing it takes 5 to 6 minutes for NEXTRAD to update when
in the base reflectivity mode.

I subscribe to two RADAR services which provide essentially the same
information. It's rare to see both systems down at the same time. If
the problem is at the NWS end then both get behind. I typically have
more complete and up-to-date information including storm track
prediction than they have at the local EOC, but like interpreting the
information on the 396 there is even more to interpret on the screens
here.

Also I base my statements on what the researcher said about the next
generation RADAR versus the current as well as conversations with NWS
people at Sky Warn training sessions as well as descriptions as to how
NEXTRAD works. IE, it updates about every 10 minutes in clear air
mode and every 5 to 6 minutes in the base reflectivity mode.

>whomever's in control of the processing is introducing the delay so they can
>sell seconds old data as a premium service.

As far as I know the processing is all done by the NWS with only the
inherent processing delay. There is the processing delay and then
there is the delay that is introduced to those images that are
provided free and has nothing to do with the processing delay. IE they
just aren't put up as soon as the ones we pay for.

I already pay that premium as does the satellite service for the
images down linked to the 396.

The important thing to remember is that NEXTRAD "does not produce real
time images!" Period. For confirmation of that just go to the NWS
site for the explanation as to how NEXTRAD works.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>Jon
>

Roger

June 13th 06, 08:58 AM

On Mon, 12 Jun 2006 06:16:21 -0700, Sam Spade >
wrote:

>Roger wrote:
>
>> On 9 Jun 2006 17:04:28 -0700, "Robert M. Gary" >
>> wrote:
>
>>
>> The 396 has some advantages and disadvantages when compared to
>> airborne RADAR. Starting with the good, it does not have the blind
>> spots you will find from time to time in airborne RADAR caused by
>> absorption in heavy precipitation which can hide some nasty stuff.
>> OTOH if you keep in mind that the display is probably 5 minutes old or
>> a tad more AND you have been following it you can pick your course.
>
>All systems have their limitations, including airborne weather radar.
>That is the reason that the prudent operation of airborne weather radar
>requires minimim avoidance distances, depending upon altitude and
>weather the outside air temp is above freezing.
>
>The limitation you cite indeed exists but can be avoided through use of
>distance-to-avoid parameters and not pushing the envelope to get the

But again in the context of the OP it takes experience to realize
these things exist.

When you see a line and particularly a bow that starts out green on
your side, then yellow and then red followed by nothing it's time to
go some where else. That is no guarantee that sever weather exists
behind that line but it's a good indicator.

Like you and others have said, being conservative, using all available
information, and education are the important items.

>mission accomplished, so to speak. The EAL wind shear crash at JFK, the
>Delta L-1011 wind shear crash at DFW, and the Soutern Airways DC-9 crash
>in southern Georgia all happaned when penetration rather than avoidance
>was attempted..

When this stuff can take the "big boys" down the smaller stuff should
be some where else entirely.

>
>The ideal setup in high-end aircraft today is airborne radar with the
>largest feasible antenna and piped in weather radar for planning
>purposes. The latter doesn't work in much of the world, though, just
>like the 396 won't provide weather outside the 48 states.

There are areas where it won't do that good a job inside the US
either, but for the most part it can be a very useful tool,
particularly when used in conjunction with other available
information.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger

June 13th 06, 09:02 AM

On Mon, 12 Jun 2006 09:24:27 -0400, Dave Butler > wrote:

>Dan wrote:
>> For those of you with a Garmin 396, how do you avoid dangerous weather,
>> avoid yellow and steer clear of the lightning strike indications? I am
>> considering the purchase of one and am wondering how to use the info
>> safely, but yet with the maximum utility.
>
>I just want to add to those who suggested getting your feet wet a little at a
>time and using the 396 information conservatively until you have some experience
>with it:
>
>The 396 I think still comes with the automobile kit, so on a day with some
>active weather you can stick the 396 in your car and drive around looking for
>interesting conditions. Its' a lot cheaper and safer to experiment in your car.

Not necessiarily if you go storm chasing like I often do. <:-))

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>Dave

Sam Spade

June 14th 06, 12:45 AM

Roger wrote:

>
> Not necessiarily if you go storm chasing like I often do. <:-))
>
>
You must live in OK or KS?

That sport looks very interesting provided a reasonable amount of
caution is used.

Roger

June 14th 06, 07:24 AM

On Tue, 13 Jun 2006 16:45:32 -0700, Sam Spade >
wrote:

>Roger wrote:
>
>>
>> Not necessiarily if you go storm chasing like I often do. <:-))
>>
>>
>You must live in OK or KS?

Just in the plain old lower peninsular of Michigan.
We get quite a few, but typically they only last 5 to 10 minutes which
means by the time the warning goes out they usually have also. Most
of the ones we get are on the order of F-2s or so, but way back in the
50's we had the F-5 Beecher Tornado on the north side of Flint.
>
>That sport looks very interesting provided a reasonable amount of
>caution is used.

That's one of the reasons those of us who go out on the road like
timely RADAR updates and make it a practice to try and stay behind a
storm. There are a lot of trees even along the main roads so
visibility can often be limited right in your direction of interest.

You lean to drive with one eye on the sky, one on the road, and one
looking for cover...just in case.<:-))

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com