Faith in ADSB weather

[Tim Jodice 263]

This is a picture of Fore Flight with a look outside. Fore Flight shows what should be pretty bad weather yet as you can see looking outside it is nice VFR weather.

I am disappointed because now when I see red I dont know if it is for real. Fortunately approach is always very helpful avoiding the heavy stuff.

According to Fore Flight the ADSB information is 9 minutes old and the depicted weather is about 40 miles it goes well past the outer ring of the bravo airspace in all directions.

Even if  the weather information was old, given the size I would think have had to go through something. Yet at most it was light rain that you can see through. 

With all of that said I am looking for advice as to how to use this information. Currently I think it is almost useless. 

 

[ArtVandelay 2,547]

I’ve never seen it that bad. But it really doesn’t tell you at what altitude the rain is at, Sometimes it shows rain but it’s just thicker higher clouds. But it’s usually green, maybe a little yellow, but not red. Maybe someone can look at the historical images and see what went wrong.

[201Steve 162]

I have found it to be relatively accurate myself.

[carusoam 12,477]

Great question with pics...

Lets see if our weather guy has any insight for variations between reality and ADSB displayed... @Scott Dennstaedt
 

Tim,  Where and when is the data coming from?

Best regards,

-a-

[toto 426]

I've definitely had a few times where the ADS-B radar view disagreed with the window.  Once in particular, the FIS-B nexrad view on the GTN (which was the same on my tablet) showed that we were entering an area of moderate precipitation, and we were flying right at the freezing level.  I was listening carefully to other aircraft on an approach frequency, and no one mentioned precipitation.  I asked approach twice whether they had had any reports of precipitation, and they said no (but they were very interested to know if we had encountered precip, since their radar was showing nothing).

Out of an abundance of caution, we descended about 3k ft to get temps well above freezing.  Flew for more than an hour in moderate precip on the GTN/tablet displays, but never saw a drop of anything out (or on) the window.  We were in continuous FIS-B coverage, and it just kept disagreeing with reality.

For what it's worth, if I saw heavy/extreme FIS-B precip on the GTN at night, I'd probably divert and call it a day.  But I have seen some strange FIS-B displays, and it's not an experience I ever had previously in the XM world.

[Tim Jodice 263]

13 minutes ago, carusoam said:

Great question with pics...

Lets see if our weather guy has any insight for variations between reality and ADSB displayed... @Scott Dennstaedt
 

Tim,  Where and when is the data coming from?

Best regards,

-a-

Boston area

https://flightaware.com/live/flight/N5812T/history/20200723/0025Z/KACK/KMHT

[Tim Jodice 263]

12 minutes ago, toto said:

For what it's worth, if I saw heavy/extreme FIS-B precip on the GTN at night, I'd probably divert and call it a day.  But I have seen some strange FIS-B displays, and it's not an experience I ever had previously in the XM world.

I would have turned around if:

I didn't have unlimited VFR visibility 

ATC advised me of weather that matched what ADSB was showing me

Other aircraft were reporting weather.

Yet that entire flight might have had minutes of MVFR.

[N201MKTurbo 5,659]

Back in the ‘80s when I was flying a lot of IFR. I was flying to KRAP a lot. There was a NWS radar site at the airport. 
 

One day I wondered over to the radar station and asked what was going on weather wise. The old guy there took me back and spent an hour or so teaching me how to operate the NWS weather radar. After that, if I stoped in, he would let me know if 5he radar was on line or not. If it was on line, he would take it off line a let me use it.

The deal is the elevation angle. You can measure the tops and bottom of the rain by looking at the azimuth and distance and then scan the elevation to measure the height at a particular distance. 

This is great while you are sitting at the console driving the antenna, but when they put it on line, which is what you see on ForeFlight and ADS-B is wherever the operator left the elevation at. If they set it to the lowest setting, you are seeing the ground. If there is a level of verga out there and they left the elevation pointed at that, that is what you see.

Government workers Being lazy or inattentive, who would have thunk? 
 

 

[toto 426]

Just now, Tim Jodice said:

I would have turned around if:

I didn't have unlimited VFR visibility 

ATC advised me of weather that matched what ADSB was showing me

Other aircraft were reporting weather.

Yet that entire flight might have had minutes of MVFR.

Yep, understood. I wasn't being critical - just thinking out loud. I've had some experiences near storms at night where I thought I had a very good view of the weather out the window and was then surprised at the actual shape of the thing. 

[Tim Jodice 263]

11 minutes ago, toto said:

Yep, understood. I wasn't being critical - just thinking out loud. I've had some experiences near storms at night where I thought I had a very good view of the weather out the window and was then surprised at the actual shape of the thing. 

I didn't take it that way .

There have been times that it was green on the screen and approach advised me of moderate to severe precipitation and vectored me around it. That happened rather frequently. 

Then there are times that what is on the screen that matches exactly what I am seeing, approach is advising and other aircraft are talking about and avoiding.  Like this one.

https://flightaware.com/live/flight/N5812T/history/20200723/2215Z/KACK/KMHT

[carusoam 12,477]

I can’t think of a better answer to the where and when question.... 

 

And I grabbed this one by the tail...

-a-

 

[gsxrpilot 11,753]

I've had very good and accurate results from ADSB weather. 

I noticed in the OP's pic we only see the ground. What about the sky? Did you have stars overhead? You might have been below all the shit being displayed by ADSB.

[Tim Jodice 263]

Just now, gsxrpilot said:

I've had very good and accurate results from ADSB weather. 

I noticed in the OP's pic we only see the ground. What about the sky? Did you have stars overhead? You might have been below all the shit being displayed by ADSB.

I don't remember if I could see stars. If it was above me why wasn't heavy rain coming down on me? 

[EricJ 2,567]

I've found it very useful as well, and accurate enough to be a lot of help.   Even live on-board radar has limitations, so there are no situations I'm aware of where you don't have to use some judgement and interpretation skills.   Even looking out the window at isolated cells is limited because you can't see inside and your eyeball is not accurate for distance measurement.

I'm always a bit surprised at some of the things that people find to complain about, and ADS-B weather is one of them.   I think it's a wonderful tool that's free to anybody with a receiver and an EFB to display it on.

 

[MooneyMark 95]

6 hours ago, N201MKTurbo said:

... This is great while you are sitting at the console driving the antenna, but when they put it on line, which is what you see on ForeFlight and ADS-B is wherever the operator left the elevation at. If they set it to the lowest setting, you are seeing the ground. If there is a level of verga out there and they left the elevation pointed at that, that is what you see.....

Interesting! Never looked at it that way, but that makes sense.

No ADS-B weather here in Europe, so I have nothing to complain about.

[Tim Jodice 263]

5 hours ago, EricJ said:

I'm always a bit surprised at some of the things that people find to complain about, and ADS-B weather is one of them.   I think it's a wonderful tool that's free to anybody with a receiver and an EFB to display it on.

 

I didn't look at it that way. To counter my complaint I think the traffic is fantastic and even if it didn't have any weather i would still use it for traffic alone. 

It is simply discouraging that I can fly through a area that is covered in yellow and red yet look out and it is VFR.

[David Lloyd 505]

Sitting at home in light rain, look at the weather radar on the weather channel.  Sometimes it looks like your house might wash away, other times it looks accurate for what you experience.  The local news and weather, if they have their own radar almost always shows heavier rain that what actually happening (maybe this attracts viewers).  If it really is raining hard, the weather channel or Channel 9 appears pretty accurate.  Seems like the same thing is going on with the NWS radar; make the picture ugly as possible.

Most of my flying life, my Stormscope kept me out of the thunderstorms, the big bumps. I have flown through very heavy rain with a smooth ride and nothing showing on the Stormscope. Wife and passengers do not like that and it wears the paint off the leading edges.

[1001001 61]

12 hours ago, Tim Jodice said:

This is a picture of Fore Flight with a look outside. Fore Flight shows what should be pretty bad weather yet as you can see looking outside it is nice VFR weather.

I am disappointed because now when I see red I dont know if it is for real. Fortunately approach is always very helpful avoiding the heavy stuff.

According to Fore Flight the ADSB information is 9 minutes old and the depicted weather is about 40 miles it goes well past the outer ring of the bravo airspace in all directions.

Even if  the weather information was old, given the size I would think have had to go through something. Yet at most it was light rain that you can see through. 

With all of that said I am looking for advice as to how to use this information. Currently I think it is almost useless. 

 

Is your display set to show both composite and base data?  It's not just ADS-B; anyone who looks at NEXRAD data will see the same thing. 

As others have mentioned, it's necessary to look at the age of the data.  But also, depending on the distance from the radar station, the composite picture can show moisture that is at high altitudes but not reaching down to your flight altitude.

[1001001 61]

9 hours ago, Tim Jodice said:

I don't remember if I could see stars. If it was above me why wasn't heavy rain coming down on me? 

Could have been virga.

[CharlesHuddleston 123]

As mentioned above, its good to know if it is a composite picture, or single slice of the radar. As others have mentioned, the radar will bounce signals off the moisture in the air, not necessarily precipitation. With a good view of the ground as you had, I would suspect everything that was showing up on the radar was building above. What was the current ATIS or AWOS at the airport? That is usually a more precise measure of what is going on at that exact moment. What about the winds and/or the direction of the winds? Again, with old info, could it have been blowing through before you got there? There are certainly a lot of variable in play here that could explain what was shown versus what was on the radar composite. One thing I have learned from reading, studying, and listening to those with more grey hair (experience) would be to consider a strike finder if you are looking at options for better in-cockpit awareness. 

Couple weeks ago, I was flying back from Key west with my family, and basically had to pick my way through the cells. Fortunately it was during the day! I used a combination of advice from ATC, the ADSB picture, Strike Finder details, and simple VFR flying to avoid the clouds. We were at 11,500, and honestly a lot of what was showing up was either at or below us. The bigger stuff was easier to avoid. 

Bottom line is to know your personal comfort zone, and be able to use all the resources available to help guide you through the sky. Stay safe and happy flying!

Edited August 17, 2020 by CharlesHuddleston
added pic

[Tim Jodice 263]

1 hour ago, CharlesHuddleston said:

One thing I have learned from reading, studying, and listening to those with more grey hair (experience) would be to consider a strike finder if you are looking at options for better in-cockpit awareness. 

Bottom line is to know your personal comfort zone, and be able to use all the resources available to help guide you through the sky. Stay safe and happy flying!

 

 

I have a WX10. Having that is another reason I kept going. It was blank.

I fly frequently through the same area so my personal comfort zone is higher than most.

[Hank 8,253]

7 hours ago, CharlesHuddleston said:

As mentioned above, its good to know if it is a composite picture, or single slice of the radar. As others have mentioned, the radar will bounce signals off the moisture in the air, not necessarily precipitation. With a good view of the ground as you had, I would suspect everything that was showing up on the radar was building above. What was the current ATIS or AWOS at the airport? That is usually a more precise measure of what is going on at that exact moment. What about the winds and/or the direction of the winds? Again, with old info, could it have been blowing through before you got there? There are certainly a lot of variable in play here that could explain what was shown versus what was on the radar composite. One thing I have learned from reading, studying, and listening to those with more grey hair (experience) would be to consider a strike finder if you are looking at options for better in-cockpit awareness. 

Couple weeks ago, I was flying back from Key west with my family, and basically had to pick my way through the cells. Fortunately it was during the day! I used a combination of advice from ATC, the ADSB picture, Strike Finder details, and simple VFR flying to avoid the clouds. We were at 11,500, and honestly a lot of what was showing up was either at or below us. The bigger stuff was easier to avoid. 

Bottom line is to know your personal comfort zone, and be able to use all the resources available to help guide you through the sky. Stay safe and happy flying!

Nice details, Charles. You went almost over my house . . . 

Just realize that the time stamp in the ADS-B picture is the time it was broadcast, and is typically 15-20 minutes AFTER the radar data was captured, to allow time to create a composite picture from multiple radar sites and prep it for distribution. Your StormScope is live data, centered on your plane. 10-minute-old ADS-B weather may actually be a half hour old, and the red will be well away from where it is depicted.

Edited August 17, 2020 by Hank

[GeeBee 999]

https://www.aopa.org/news-and-media/all-news/2012/june/25/ntsb-warns-of-in-cockpit-weather-delays

It does not matter what the age on the screen says, there are other latencies in the system not noted.

I was near SPA the other days dodging T-Storms from an off shore hurricane. As I looked straight ahead I saw a large black CB, the XM said nothing there.  The ADS-B on the iPad said, nope, but there was a big black CB ahead and blue sky to the left where both units showed a cell. LATENCY. Remember,  one peek is worth a thousand sweeps. These services are strategic, not tactical. For tactical you need real time on board radar.

 

[Scott Dennstaedt 313]

On 8/16/2020 at 9:39 PM, carusoam said:

Great question with pics...

Lets see if our weather guy has any insight for variations between reality and ADSB displayed... @Scott Dennstaedt
 

Tim,  Where and when is the data coming from?

Best regards,

-a-

Sorry I'm a bit late to the game...lots going in these days and don't get much of a chance to participate. 

There's certainly a lot to unpack in this thread and I won't specifically respond to every post, but let's first understand that every weather product or service has its limitations. Every distribution system has it's limitations. Take some time to learn those.   

First, the preflight portion of a flight is critical to understanding what you see or don't see on your in-cockpit devices. Surprises should be rare.  Second, I rarely ever zoom in on an area with a radar mosaic.  I have my display zoomed out such that I can understand the organization of the weather and how it matches with my preflight analysis. This helps to understand the trends of the intensity and development or dissipation.  Turns out in this situation, that is the key. Third, the FIS-B radar depiction is a composite reflectivity mosaic that recently was switched to using MRMS which I discussed in my blog over a year ago. The regional mosaic data is broadcast and updated every two minutes. This likely the most superior and fresh radar mosaic available today in the cockpit. Even so, it does have real limitations and should always be used as a gross vectoring aid and never used tactically to maneuver through weather.  

For Tim's original post, there's no way for me to specifically comment on the actual issue you faced. I don't comment on anything associated with FF anyway, and I wasn't in the cockpit and don't really have specific explanation on what you were seeing.  However, using the date/time of the flight, it's pretty easy to see what was going on.  There was a convective SIGMET issued to the west of the route at 2355Z (7:55 pm).

By 0055Z (8:55 pm) or shortly after departure, the convective SIGMET was still to the west of your route. These areas of thunderstorms had tops above FL450. 

 

 

By 0155Z (9:55 pm), the convective SIGMET was expanded to connect to the convective SIGMET to the south and the eastern edge covered the route.  Most of the significant convection at this point was to the south.

 

This matches well with the IR satellite image.  Note the deep blue/purple tops marking the convective area outlined by the two earlier convective SIGMETs above. These are cold cloud tops indicative of deep, moist convection.

With time, these cells began to dissipate creating what is called a convective debris shield which is often characterized with light to moderate stratiform-type rain sometimes with occasional intra-cloud lightning (FIS-B lightning doesn't show intra-cloud lightning, but SiriusXM does). So the dBZ levels can be in the 40-45 range and may often look pretty ominous, but the cellular structure wasn't present.  You can see the cloud tops began to warm as this transition occurred (more lighter blue and no purple).  

Here's the radar mosaic (not the MRMS version), but it clearly shows some fairly moderate returns from this stratiform-type rain falling throughout the destination airport. But the cellular structure is gone.

The moral of the story is to understand the limitations of the devices you are using and know what colors represent what level of dBZ (reflectivity). Those colors you see are very dependent on the vendor providing the service and they can be different. Each vendor chooses how to present this depiction (color to dBZ). 

Hope this helps.

 

Edited August 30, 2020 by Scott Dennstaedt

[carusoam 12,477]

Scott,

You are the best!

Thank you for sharing your detailed insight with us at MS!
 

Best regards,

-a-