rdrobson wrote: ↑Fri May 24, 2019 4:19 pm
You're right that the data is not live, but it's not 15 minutes old either.
But it pretty much is:
In June 2012, the NTSB issued Safety Alert SA-017 (amended in December 2015), which asserted that cockpit imagery could be 15 to 20 minutes older than the posted time: https://www.ntsb.gov/safety/safety-aler ... SA_017.pdf
I do not want readers of this forum to get the wrong impression that NEXRAD in any form is a safe reference to dodge rapidly moving and building thunderstorms.
jb642DA wrote: ↑Sat May 25, 2019 2:32 am
I still remember a "mission statement" from 30+ years ago when I was in the USAF - "There is no peacetime mission that requires the penetration of a thunderstorm!"
(note the word "peacetime"! - more YIKES)
Well, there is one mission. Way back when I was in college, one of my professors had an old Air Force friend who routinely flew into thunderstorms (along with the hail, lightning and tornadoes that go along with the rain and turbulence) and he would tell us stories from those flights. Of course, he had special equipment to make it safe.
rdrobson wrote: ↑Fri May 24, 2019 4:19 pm
You're right that the data is not live, but it's not 15 minutes old either.
But it pretty much is:
In June 2012, the NTSB issued Safety Alert SA-017 (amended in December 2015), which asserted that cockpit imagery could be 15 to 20 minutes older than the posted time: https://www.ntsb.gov/safety/safety-aler ... SA_017.pdf
Maybe I should clarify a bit, in the situation I described I was able to track several isolated cells while in VMC as they passed landmarks and compare what I saw out of the windshield with what XM was putting on the screen. On that day, the delay was far less than 15 minutes and I would guess it was less than 5 minutes. However, that's not to say that in other cases it may be worse. Maybe the continental US only had a few storms so they could focus their bandwidth on what I was looking at. I agree completely that if you can't visualize the storm via tactical methods, XM is only there to keep you clear of the entire area. It is especially helpful when you have it display storm tracks as well so you can get a good sense of how the system is moving and hopefully stay on the backside of the movement.
rdrobson wrote: ↑Wed May 29, 2019 1:25 am.... On that day, the delay was far less than 15 minutes and I would guess it was less than 5 minutes....
That time stamp only reflects how long ago either Sirius/XM or ADSBIN sent out its most recent (already old) information. How long it took to aggregate that information to build the NEXRAD picture and send it to Sirius/XM or ADSB-IN is unknown. I assume as much as 15 minutes, since the time stamp is seldom more than 5 minutes, and 15 + 5 equals the "up to 20 minutes" stated in the Safety Alert.
rdrobson wrote: ↑Wed May 29, 2019 1:25 am.... On that day, the delay was far less than 15 minutes and I would guess it was less than 5 minutes....
That time stamp only reflects how long ago either Sirius/XM or ADSBIN sent out its most recent (already old) information.
Sorry, I wasn't clear as to what I was referring to. I was not looking at the timestamp on the G1000 display. I was looking at what XM was plotting as the cell location vs what I could easily see with my eyes. I was at low altitude in VMC just a few miles from KUGN so it was very easy to compare the actual real time location of the cells to what XM was displaying as the cells moved right across KUGN. There was no where near a 15 minute lag from the actual to displayed location of these cells. But as I mentioned previously, perhaps the 15-20 minute delay is a worst case situation, I really don't know.
jb642DA wrote: ↑Sat May 25, 2019 2:32 am
I still remember a "mission statement" from 30+ years ago when I was in the USAF - "There is no peacetime mission that requires the penetration of a thunderstorm!"
(note the word "peacetime"! - more YIKES)
Well, there is one mission. Way back when I was in college, one of my professors had an old Air Force friend who routinely flew into thunderstorms (along with the hail, lightning and tornadoes that go along with the rain and turbulence) and he would tell us stories from those flights. Of course, he had special equipment to make it safe.
The T28 article is "wild" - those must have been "fun flights"!!
There are USAF guys/gals that do "play with/penetrate" thunderstorms - the huricane hunters are one of those groups.
My comment was relating to my group (wing). I was flying the F15 at that time.
My point is - don't "mess" with thunderstorms! They are incredibly dangerous.
Last edited by jb642DA on Thu May 30, 2019 1:41 am, edited 1 time in total.