NEXRAD Refresh Rate?

Discussion in 'Flight Following' started by JC150, Sep 11, 2015.

  1. JC150

    JC150 Pre-takeoff checklist

    Joined:
    Apr 22, 2013
    Messages:
    488
    Display Name:

    Display name:
    JC150
    I did a forum search, and couldn't find what I was looking for...

    For those of you that use Nexrad, which receiver do you have and how often does it refresh for you?

    I have a Garmin Aera in my plane with Nexrad, but I've had images as old as 45 minutes.

    I currently have a GNS530 and a Aspen PFD in my plane and I'm thinking about adding a weather receiver so I can have faster image refresh rates. My options are to add a GDL69 to the GNS530 or an EWR50 to the Aspen.

    Does anyone have either the GDL69 or EWR50 that can chime in on what kind of NEXRAD refresh rates they're getting? Thank You
     
  2. KyleT

    KyleT Pre-takeoff checklist

    Joined:
    Dec 18, 2011
    Messages:
    130
    Location:
    DFW TX
    Display Name:

    Display name:
    1kilotango
    Not sure how fast the upload rate is, but the broadcast age is at least 5-7 mins old as that is about how long it takes to sweep the different azimuths and process the image.
    https://en.m.wikipedia.org/wiki/NEXRAD explains it more.


    Sent from my iPhone using Tapatalk
     
  3. TulsaWeather

    TulsaWeather Pre-takeoff checklist

    Joined:
    Jun 16, 2007
    Messages:
    167
    Location:
    Tulsa
    Display Name:

    Display name:
    TulsaWeather
    The product is a composite of the single-site Nexrad "composite reflectivity" product. That takes a whole volume scan to render, then national product is generated and transmitted.
     
  4. Luigi

    Luigi Line Up and Wait

    Joined:
    Jan 13, 2013
    Messages:
    510
    Display Name:

    Display name:
    Luigi
    How often does XM satellite cloud cover info refresh, and how old is the data upon reception?
     
  5. Velocity173

    Velocity173 Touchdown! Greaser! PoA Supporter

    Joined:
    Jul 3, 2012
    Messages:
    12,361
    Display Name:

    Display name:
    Velocity173
    We have a GDL 69 in our aircraft. 5-7 minutes but can be up to 20 minutes old. A few times this summer I saw developing storms visually but didn't show up on the 530. Had ATC point out a storm in front with "moderate precip." I had nothing in the 530. A minute later, a green and yellow return showed up 5 miles in front of me.
     
  6. Unit74

    Unit74 Final Approach

    Joined:
    Mar 8, 2014
    Messages:
    6,632
    Display Name:

    Display name:
    Unit74
    Is put it on the 530. The PFD is just too small for that. It will work, but very small.
     
  7. James331

    James331 Ejection Handle Pulled

    Joined:
    Apr 18, 2014
    Messages:
    20,310
    Display Name:

    Display name:
    James331
    That.

    I wouldn't spend much money on it, IMO NEXRAD and whatnot are great for big picture planning, but not nearly fast enough or reliable enough for tactical use, for that stuff you really need your own onboard radar.

    Work plane has onboard radar and XM, sometimes there is a decent difference, I've also had ATC warn me of things which were no longer there, and worse not see things that were there.
     
  8. Sundancer

    Sundancer En-Route

    Joined:
    Aug 16, 2015
    Messages:
    2,986
    Display Name:

    Display name:
    Sundog
    T-Storms can build faster than the refresh rate. A lot faster! Clear air to bad-boy in as little as five minutes. I've never seen our Aera 45 minutes old, though. I use it to see where the giant gaps are, pick an escape/evasion route, or if there aren't any, to call it a day.

    I mean I really like having it, but as the previous poster said, not a real-time tactical tool. . .
     
  9. wilkersk

    wilkersk Pattern Altitude

    Joined:
    May 21, 2015
    Messages:
    1,893
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    How long does it take for a whole volume scan to render, then reconstruct the composite? Is that all automatic, or does someone have to intervene regularly? How often do those post-processing algorithms get tweaked?
     
  10. pilotjlr

    pilotjlr Pre-Flight

    Joined:
    Jan 2, 2014
    Messages:
    36
    Display Name:

    Display name:
    james
    It's important to bear in mind the refresh rate varies based on conditions. In "storm mode", it should only be about 5 minutes. It seems to be a persistent misunderstanding that people think NEXRAD is always a 20 minute delay, but that's only true in clear air mode, when there's no precip anywhere.

    https://en.wikipedia.org/wiki/NEXRAD#Scan_strategies
     
  11. RudyP

    RudyP Line Up and Wait

    Joined:
    Nov 5, 2008
    Messages:
    999
    Location:
    SF Bay Area, CA
    Display Name:

    Display name:
    RudyP
    One point I'm not seeing here (at least very obviously) is that there are two sources of delay. One is the capture/aggregation/processing/pushing to the satellites time and the other is the how long ago did you get your last refresh time. The first can be 1-10 min (roughly, IIRC) and the second varies but that's what you will see on your display (not including the first delay). So while your WX display may show Nexrad as being 2 min old, it may actually be displaying data that was produced from scans as long as 12+ minutes ago.

    FWIW - I don't think I've ever seen more than 5-10 minutes displayed on my avionics before a refresh. This is on Garmin Perspective (G1000).

    45 Min sounds like there is a signal/antenna type issue and it's missing broadcasts.
     
  12. Bill Watson

    Bill Watson En-Route

    Joined:
    Dec 5, 2007
    Messages:
    2,555
    Location:
    Durham NC
    Display Name:

    Display name:
    MauleDriver
    This is not an answer but an unverified assumption and an unrelated suggestion FWIW:

    Assumption; there is little or no difference in Nexrad delay times relative to the equipment installed in the aircraft. Delay times vary based on external factors.

    Suggestion; rather than assessing delay times, get out there and fly with it while staying clear of clouds and figure out the value of what's displayed vis-a-vis what you see out the window. Nexrad will demonstrate itself to be the most valuable weather avoidance tool you could have in the aircraft (short of onboard radar I am told).

    And if you are already familiar with Nexrad's value, benefits and deficiencies, then install a solution that makes it available to you in a cost effective, flexible, and integrated way independent of any claims of faster refresh and such.

    Just an opinion.
     
  13. TulsaWeather

    TulsaWeather Pre-takeoff checklist

    Joined:
    Jun 16, 2007
    Messages:
    167
    Location:
    Tulsa
    Display Name:

    Display name:
    TulsaWeather
    Automatic, I'd say 60 seconds or less to build the composite. A whole volume scan depends on the "Volume Coverage Pattern" the radar is operating in. Usually, if there's precip around, it's 5-7 minutes. Can be shorter during severe weather operations.
     
    Last edited: Sep 11, 2015
  14. jaybee

    jaybee Cleared for Takeoff

    Joined:
    Jan 22, 2012
    Messages:
    1,143
    Location:
    sometimes Cocoa, FL
    Display Name:

    Display name:
    jaybee
  15. KyleT

    KyleT Pre-takeoff checklist

    Joined:
    Dec 18, 2011
    Messages:
    130
    Location:
    DFW TX
    Display Name:

    Display name:
    1kilotango
    There is a very good air safety video that talks about the delay. Air safety Institute I believe, can't remember or find it on google at the moment. I believe the delay that you see in minutes old is the time since broadcast.

    The crash was a Piper PA32 who had onboard xm, and flew into a cell because the data was not new enough. There is an image overlay showing what the primary weather radar that ATC sees vs the NEXRAD XM image the pilot saw. And the flight path.

    From non aviation related meteorology and weaver study, we were always taught to use NEXRAD as a "big picture" product to see storm structure and intensity, not for precise location. But on the ground the danger is very low.



    Sent from my iPhone using Tapatalk
     
  16. Clark1961

    Clark1961 Touchdown! Greaser!

    Joined:
    Jun 7, 2008
    Messages:
    17,746
    Display Name:

    Display name:
    Display name:
    The radar display difference is a pretty good reason to be talking to ATC and asking them what they see. The problem I've run into is when they're busy it's tough to force the question to them and tie up the freq. So far I've just taken the conservative course when things are busy. Otherwise, ATC has been a tremendous asset that is easy to use for input when making decisions.
     
  17. Bill Watson

    Bill Watson En-Route

    Joined:
    Dec 5, 2007
    Messages:
    2,555
    Location:
    Durham NC
    Display Name:

    Display name:
    MauleDriver
    Reflecting on my experience the past few months I now realize that while I exercise ATC as much as I can, I believe my eyeballs first, my eyeball calibrated Nexrad second, and ATC third.

    So the question is what do you do when trying to avoid convective activity when blind in IMC? Well, I just don't do it any longer. I stay visual in convective systems and only penetrate clouds when I can see where I come out. Nexrad has enabled that. There just hasn't been any need to fly blind among imbedded crap in my pleasure flying.

    YMMV
     
  18. Clark1961

    Clark1961 Touchdown! Greaser!

    Joined:
    Jun 7, 2008
    Messages:
    17,746
    Display Name:

    Display name:
    Display name:
    No argument at all. We sometimes get repeated thunderstorms building along the front range sort of like the gulf coast gets but it happens faster. Better be visual in that situation or have onboard radar.

    When it gets towards dark-thirty I'm trying for ATC help pretty hard. Only had to do it a few times but it's been "interesting". If there's lightning I can avoid it but if it's just mechanical turb plus building convective stuff it can be a bit of a challenge. Much better to wait for early morning and clear air.
     
  19. KyleT

    KyleT Pre-takeoff checklist

    Joined:
    Dec 18, 2011
    Messages:
    130
    Location:
    DFW TX
    Display Name:

    Display name:
    1kilotango
    Yes the avoid imc in convective activity is a good choice. But get there itis causes a lot of poor decision making and ends up taking lives.

    People don't realize that GA doesn't have the same dispatch rate as the airlines until you get up into the two pilot jets. Even then some of them will be conservative. Not that airlines aren't just the system favors the airline. They have teams that work on weather and routing to make it efficient.


    Sent from my iPhone using Tapatalk
     
  20. TEFLONSEAN

    TEFLONSEAN Line Up and Wait

    Joined:
    Oct 5, 2014
    Messages:
    604
    Display Name:

    Display name:
    Teflonsean
    ATC sees the same thing that NEXRAD does. So it's not all that great....in close.

    NEXRAD is a good tool when your far out and there is no convective activity. Close in...it will hurt you(convective or not) and there have been times when it has killed pilots.

    Unless you have onboard radar....don't go playing around close in with NEXRAD. Unless you have a death wish.

    My .02
     
  21. Clark1961

    Clark1961 Touchdown! Greaser!

    Joined:
    Jun 7, 2008
    Messages:
    17,746
    Display Name:

    Display name:
    Display name:
    ATC resources depend entirely on the type of facility. As I said there are good reasons to be talking to them. Of course talking to them is not a reason to continue looking out the window or using other resources which may be available.

    Thanks for repeating the NEXRAD mantra, I'm sure there is a chance that somebody out there hasn't heard it and might benefit from your taking the time to type it one more time.
     
  22. Velocity173

    Velocity173 Touchdown! Greaser! PoA Supporter

    Joined:
    Jul 3, 2012
    Messages:
    12,361
    Display Name:

    Display name:
    Velocity173

    Like Clark said, depends on the facility. You've got a few different systems (ASR-9, ASR-11, ASR-4)at play these days. Each of those provides a slightly different view than the typical NEXRAD WSR-88s. Not sure about center's ASR-4s but a terminal ASR-9 / 11 has a 30 sec refresh rate. That's the difference between ATC pointing out moderate precip and not having anything on your cockpit XM weather because of the delay.

    Not sure how many of the old analog ASR-8s left out there but their rate is almost instantaneous. While not as good as NEXRAD in coverage / level, I actually preferred the detail of the precip over DASR systems.
     
  23. dell30rb

    dell30rb Final Approach

    Joined:
    May 18, 2011
    Messages:
    7,117
    Location:
    Raleigh NC
    Display Name:

    Display name:
    Ren
    I keep hearing this, but after a year of working a job requiring airline travel 3-4x per month, I don't believe it. For 9 months out of the year anyway.
     
    Last edited: Sep 14, 2015
  24. RudyP

    RudyP Line Up and Wait

    Joined:
    Nov 5, 2008
    Messages:
    999
    Location:
    SF Bay Area, CA
    Display Name:

    Display name:
    RudyP
    I agree. I have only canceled 2 trips and delayed (by more than a few minutes) maybe 10 trips out of 8 years, 1900 hours and 1000+ flights. I doubt any airline can claim these statistics. And, yes, I am a very conservative weather flyer.