Topic: How long of a delay in RADAR images on various service?

[DaleReid]

I have a Windy.com and WeatherTap subscription.

I'm wondering how long the delay is from an image coming out of the RADAR, say at Minneapolis, or LaCrosse, etc, and before that image shows up in the most recent area views available on their sites?

I know that NWS provides the images to the public.  Do those commercial suppliers pay more to get faster access to the images?

Last night while some big hail and a couple of funnel clouds were happening in northern Wisconsin, the various stations were showing 'live' sweeps of the RADAR (yes there is the discussion about the fact that these are digital images, and there really is no 'sweep' but indeed the antenna DOES sweep, but I digress. As the sweep occurred it was obvious that there was a change in the reflected image, with a progression in one of the velocity plots from sweep to sweep.  I assume that this was about as real time as one can get.  But can we common folk get those types of data?

Thx for any comments. Dale

[ocala]

Dale when there is severe weather in a particular area the NWS servers get a lot of requests for data which makes them slow to update.
Getting a sub to a third party data service cures that problem. The issue is whether the program or app you use to access radar has an option to use a third party data server. I think just Radarscope and Radar Omega are the only two apps that allow it.

[DaleReid]

Thanks, that makes sense. 

Those two services  you mentioned aren't one's I"m familiar with, so I'll take a look.
Yeah, I can only imagine the amount of  interest in live or as live as  you can get, images from the NWS sites.

I was just wondering if there was, on the aveage, say 5 or 15 minutes delay.
Dale

[CW2274]

the various stations were showing 'live' sweeps of the RADAR (yes there is the discussion about the fact that these are digital images, and there really is no 'sweep' but indeed the antenna DOES sweep, but I digress.

Well, you're right, they're wrong. There is of course a sweep. How else would it work? Only thing is it's a digitized display vs a raw radar paint. When ATC facilities were being upgraded to digitized displays in the early 2000's, the work force demanded an artificial sweep to be employed to make us happy. We don't like change.   

As far as live wx radar, I remember in 1986 when I was in OKC, they dedicated a local TV channel to show live wx radar when it got severe. Sadly, the only time I've ever seen that.

[DaleReid]

The 'sweep' of a radar is so ingrained from the ideas from WWII and later that people see them as something almost stereotypical of a display like that.

The old approach radars for landing had a very fast sweep up and down.  I often marveled at the bearings and the gears taking that strain.  And the display link made sense.

Now in many, even light single engine aircraft, those big panels display the map and terrain and if you pay enough, the area radar and as you mentioned, what is displayed is the processed data which is what is important, not a 'scan' sweep.

[DoctorKnow]

I like this site. https://weather.cod.edu/satrad/?parms=subregional-Carolinas-comp_radar-24-0-100-1&checked=map&colorbar=undefined

You can click on Dual pole NEXRAD on the left and get radar images with updates as fast as every minute at times.

[CW2274]

The old approach radars for landing had a very fast sweep up and down.  I often marveled at the bearings and the gears taking that strain. 

And left and right. Called PAR (precision approach radar). I was certified on both land and sea with it in the Navy. Matter of fact, on land, C5's were so big, you'd paint the rear horizontal stabilizer along with the fuselage.

[ocala]

Thanks, that makes sense. 

Those two services  you mentioned aren't one's I"m familiar with, so I'll take a look.
Yeah, I can only imagine the amount of  interest in live or as live as  you can get, images from the NWS sites.

I was just wondering if there was, on the aveage, say 5 or 15 minutes delay.
Dale

In Clear Air Mode the update is 10 minutes. This VCP ( Volume Coverage Pattern) is used during clear weather.
In Precipitation Mode the VCP update is 5-6 minutes. I also think there is a Severe Mode used during heightened tornadic activity which updates at 3 minutes but I'm not sure about that.
Some radar apps/sites will just stick with the  10 minute updates. I am always looking for new radar apps. The first thing I check is the update times. If it's not updating at 5-6 minutes or less I move on.
Way back when they first came out I used Weather Tap exclusively. But over time they never really changed or updated any of their graphics and the customer service got worse.

[Cutty Sark Sailor]

Last year I kinda got fed up with trying to track down a radar app/source... played with, and KEPT the RADARSCOPE app, and stream it with a virtual camera to my site...  https://frankfortweather.us/01RadarFKT.php
timing seems to be typically 5-7 mins between images, has various features, including my 'favorite' -- 'favorites'.  Will swap Radar Sites in an instant, and displays WWAs etc TDWRs and Research systems.  Some 'stuff' a bit tricky streaming with virtual camera, and everyone won't go to this much trouble, or have support platforms on their local, for web site presentation, but so what...I do, up to others whatever. Yep, like it, even if it's not a 'Rolls Royce'... judge for yourself.. VERY inexpensive!!!!-----------
RE SWEEPS:  I DON'T know about current usage and systems... We, however, were using DIGITAL sweeps in the military as far back (from personal knowledge) as the Vietnam War... multiple antennas sampled time wise, for vector, alt, etc.... NO Moving antennas...

[weatherdoc]

Dale,

I've used RadarScope for years, both the phone/tablet app and Window app. I also use GRLevel3 on my PC.

As @ocala mentioned, NEXRAD radars have several Volume Coverage Patterns (VCPs). Generally, in precipitation mode it takes 5-6 minutes to scan one volume and in clear air mode it takes about 10 minutes to scan one volume. In 2104, NWS implemented Supplemental Adaptive Intra-Volume Low-Level Scan (SAILS) that allows operators to run an additional base scan during the middle of a typical (5-6 minute) volume scan. SAILS base scans occur about once every 2.5 minutes. In 2011, NWS implemented the Automated Volume Scan Evaluation and Termination (AVSET) algorithm that immediately ends a full volume scan when precipitation returns at higher scan angles drop below about 20 dBZ. Therefore, updates in less than 2.5 minutes are possible if AVSET terminates the volume scan early.

With RadarScope, I have seen updates at less than 2 minutes during thunderstorms, so I know that app is getting all the updates from NWS.

Bill

[ocala]

SAILS!!
That it Bill. I couldn't remember the acronym for it.i

[weatherdoc]

Well, I should know the acronym - I've been working with the WSR-88D since 1990. I graduated from the first WSR-88D Operations Training Course in Norman, Oklahoma in November 1990 (I'm really dating myself). I've worked with NEXRAD in the USAF, NWS, and FAA. Now I'm supporting the team led by NWS for the NEXRAD replacement. I suspect I'll retire for good long before the replacement becomes operational!

[DaleReid]

WeatherDoc:
I've never been close to a RADAR site with the newest generation radar antennas in them, and the pictures always have the radome on, so the actual revolution rate is hidden.  I recall some location antennas around airports taking a minute or so to turn, no doubt doing the scanning for traffic, and of course the ground and taxi antennas seeming to rotate at once per second or two second intervals, but not really needed to see much beyond the edge of the airport.

How fast does the antenna turn on a NEXRAD system?  From your comments one might take them to mean that the rotation rate may vary, or is it always fixed? 

To do the volume sensing, does it change the beam elevation angle and re-sweep the area a bunch of times?  I can't imagine that the antennas have the capability of scanning several elevations all at once; even the BEMEWS system with their fixed antennas but phase steering had to look at one spot at a time.  At least they didn't rotate.

Curious minds want to know!  Or maybe it's just me.
Dale

Oh, what about the 'private' Dopplers that some of the high priced TV stations have of their own, sort of like VIPER and can't recall what was out there years ago.  Maybe all those have been retired, or were too expensive to maintain for what bragging rights the stations could get.  To have essentially a free feed would go a  long way in the minds of most of the chief accounting officers.

If I recall, Vaisala made 'private' radars for awhile.

Dale

[weatherdoc]

The rotation rate varies. It's typically about 3 RPM in precipitation mode. It scans 14 elevations per volume, so 14/3 = ~4.7 minutes, which is why most volumes scans take "about 4-5 minutes". In clear air mode it only scans 5 of the lowest elevations per volume and it takes about 10 minutes, so that's about 2 RPM.

It scans one elevation per rotation. So, it starts at 0.5 deg and rotates 360 deg. Then the antenna is raised to 0.9 deg (for precip mode) and rotates another 360 deg. And so on until it reaches the highest elevation angle.

I was inside the radome at the Melbourne, FL NEXRAD while it was down for maintenance. It's a massive antenna - 28 ft diameter! At the time, the Melbourne radar was about 65 ft above ground (now it's 90 ft) and climbing the open stairs to the top with a 25-mph sea breeze was a bit unnerving.

I've been wondering about the TV station radars too. They all used smaller 5-cm (C-band) radars and those that had them used to tout them as something unique. But I can't recall a TV station mentioning their own radar in many years. All the DC TV stations show NEXRAD, although some seem to indicate they are using the Dulles, National, and Baltimore TDWRs, which I doubt, but they do show the TDWR locations on their map as if they're integrating the data. Oh, and they often show the "fake" radar sweeps zipping around the radars.

Enterprise also made radars for TV stations. Before I left Florida in 2015, the 45th Weather Squadron at Cape Canaveral purchased and installed a new C-band Doppler radar that replaced an old WSR-74C (from 1974) at Patrick AFB. The new radar was positioned west of the Space Center to be able to better see the sea breeze since Doppler "sees" wind perpendicular to the radar and the old Patrick AFB radar was parallel to the coast and south of the Space Center, as is the NEXRAD at Melbourne. The new radar gave us excellent depictions of the sea breeze and outflow boundaries.

There's a company called Climavision (https://climavision.com/) that is deploying 3-cm (X-band) radars as low-altitude gap fillers for the NEXRADs. They started installing them around Charlotte, NC last spring and have continued to expand their network (see the "press releases" section of their website). Their business model is to build and maintain the network and charge users for the data.

[DaleReid]

A wonderful discussion of the techniques and equipment.  Who doesn't love weather equipment?

The information about how the primary sensor, the antenna itself, works is something I've not seen, or if I have I'd forgotten the details. 

I have a hard time going up inside enclosed walkways, say nothing of those showing more of the surrounding area like a tower.  As a kid I made it up some fire towers on tops of big hills and enjoyed the view but getting there left some of my fingerprints in the metal ladder.  I'm also glad you got to go up there, and the unit was not running.  When I was in high school in the 1960s, our science teacher was an electronics guy from the Air Force, and he described, and I don't think he was fibbing, being on a flat roofed building with a big circle painted on the roof, with orders to not get closer to the antenna than that circle when the unit was operating.  He didn't, but said one guy did and reported feeling 'funny' as the antenna pointed at him.  And then I learned about Amana RadarRangers....

I'm sure we are boring a great many who read this thread, but the equipment up in the air is one thing, but how about the goodies downstairs?  Was it all a dedicated electronics computer to ingest and process the data?  Do they use some commercial general purpose computers to work the data?  I'd think it would be on the computational scale of medical CT or MRI equipment where enormous numbers of 3-d models need to be processed.

And while the most reliable tech we've ever had is now fading away (Mother Bell's land line telephone network) these critical installations seem to just keep working, with only occasional notes that they are offline, which now that I think of it, I don't recall seeing any in years after the big upgrade effort over the last decade.

Thanks again for all the 'inside the dome' information.  This forum is great for people with wide ranges of experience having shared their info and knowledge. Dale

[CW2274]

I recall some location antennas around airports taking a minute or so to turn, no doubt doing the scanning for traffic, and of course the ground and taxi antennas seeming to rotate at once per second or two second intervals, but not really needed to see much beyond the edge of the airport.

ASDE. The faster the rotation, the faster the update, which is critical in airport operations where literal seconds is the rule of law, especially when no one can see out the window. ASR (terminal approach radar), sees out about 57nm and rotates 360 degrees in about 4.5 seconds. ARSR (ARTCC radar), sees out ~240nm IIRC, and the sweep is super slow. Don't recall the rate.

[DaleReid]

CW:
I think the vertical sweep for the old radar guided approaches was very fast, several sweeps per second.

My IFR instructor and I used to find a slow evening and go over to Truax Field/ Madison, WI and ask if they would have time to have us do a few approaches.  I never knew of other locations that I went to which had that equipment.  They didn't get much opportunity and usually bent over backwards to run us down the glideslope a few times.

anyway, I still am fascinated by RADAR of any sort.  I know some local TV stations which had old military units from decades ago as their basic stuff.  The advent of digital and all the magic that the programmers can do made that pretty old fashioned.  As WxDoc said, I don't know of any major city stations which advertise they have their own sets any more, no matter how new and expensive they were.  But I don't get out much any more and they may be more common than I know of.

I've often thought of trying to get a used but functional airborne radar set and setting it up, but no doubt have trouble getting the license for the transmitter passed when I list it being installed on my 1947 Champ....

[CW2274]

CW:
I think the vertical sweep for the old radar guided approaches was very fast, several sweeps per second.

My IFR instructor and I used to find a slow evening and go over to Truax Field/ Madison, WI and ask if they would have time to have us do a few approaches.  I never knew of other locations that I went to which had that equipment. 

Yes, the PAR antennas sweep about that, not just vertical, but horizontal as well. Been a very long time since I ran one...1982 to be exact, and was certified down to 20 feet. DMA AFB ran PAR's, which they did from my TRACON, and would occasionally let a "dink" run one, traffic permitting, but only to a restricted low approach to usually 500AGL before they had to break it off. Didn't want them to "see" anything..    Regardless, it was well received when allowed.

[TheBushPilot]

I did not think this thread would get this interesting. Wow.

Dale you mention TV stations utilizing their own personal doppler radars. From what I understand, the legacy radars were too costly to run and maintain so most sit dormant or have been taken down. That may change in the coming years with solid state technology. I have a friend that works as a broadcast meteorologist for a -I'm not even sure what you would call that yet- it's a webcast news station that utilizes their own Furuno X-band radar. FWLX at Tennessee Valley Weather is the name if I recall correctly. Super interesting how these companies are popping up and filling in the radar gaps.

Climavision is a prominent player in this game, I hear all my friends complain about their pay for data approach. I kind of agree with them. What good is data if you can't view it. FWLX and multiple other (I guess privately owned) radars have their feeds into GRLevel2 Analyst etc. Believe the Furuno is integrated into the Iowa State University Level II data feed for free as well.

Extremely interesting seeing how everything is evolving.

I also learned the other day that my boss used to calibrate FAA and NEXRAD radar equipment across the country when he was in the Air Force.

Radar is interesting lol.


Cheers

[weatherdoc]

but how about the goodies downstairs?  Was it all a dedicated electronics computer to ingest and process the data?

I think everything runs on PCs with Linux OS now. Back when the radars were first deployed they had separate racks for the Radar Data Acquisition (RDA) and Radar Products Generator (RPG). The user interface was the Principal User Processor (PUP). One thing I clearly remember is that they had this new-fangled device inside one of the racks called an optical disc drive, which was just a CD but in 1990 that was pretty cool. The PUP had a device called a puck, which was an optical mouse that we used to point and click at products we wanted to display. The RDA sends reflectivity, velocity, spectrum width, differential reflectivity, correlation coefficient and differential phase to the RPG which creates base products and runs the algorithms that generate meteorological and hydrological products.

From an FAA perspective, over the past year, we finished a project called Terminal Precipitation on the Glass (TPoG) at the request of air traffic controllers to have a better source of weather radar data on their screens. We tested multiple sources of radar data to include the ASRs weather channel, TDWRs, and NEXRADs. After much testing with controllers, we settled on NEXRAD data, even though it doesn't scan nearly as fast as the ASRs but it provides a much higher quality weather depiction. The FAA is now at the stage of transitioning the capability to operations.

[ocala]

This thread is the equivalent of radar porn for me.
Love this stuff.

[CW2274]

but how about the goodies downstairs?  Was it all a dedicated electronics computer to ingest and process the data?

After much testing with controllers, we settled on NEXRAD data, even though it doesn't scan nearly as fast as the ASRs but it provides a much higher quality weather depiction. The FAA is now at the stage of transitioning the capability to operations.

ASR 9's and up displayed six levels of digitized weather. Far cry from the ASR 5 that we basically selected circular polarization when it got too obstructive to see the screen as well as one would like. Even with the digitized weather, many times I'd have air-carrier flight crews not want the vector around I supplied due to poor resolution. This sounds like a much better way.