Gregg,
Thank you very much for this detailed explanation of the METAR data flow — this
is incredibly helpful and aligns with what we've observed from benchmarking
multiple sources.
We've been polling TGFTP at 1-second intervals with If-Modified-Since headers
and it is indeed our fastest source, consistent with your assessment. We looked
into LDM/IDD through Unidata but were unable to obtain access, and SBN/NOAAPORT
satellite ingest is more hardware investment than we can justify at this stage.
Two questions if you don't mind:
1. EMWIN terrestrial server — since it's push-based, it could shave off the
polling latency we have on TGFTP. Could you point us toward the hostname/port
of the terrestrial EMWIN server, and whether it carries METAR from all ASOS
sites? Any documentation on the connection protocol would be greatly
appreciated.
2. SynopticData's FAA agreement — we use the Synoptic API and it sometimes
detects new observations before TGFTP in our benchmarks. Do you know if their
FAA connection gives them a tap upstream of NWSTG/GATEWAY, or is it the same
pipeline?
Best regards,
Le mardi 17 mars 2026 à 18:15, Gregory Grosshans <gregory.grosshans@xxxxxxxx> a
écrit :
> At a high level the flow of METAR data from ASOS sites at U.S. Airports
> traverse the FAA networks to the NWS NWSTG/GATEWAY system. Once at
> NWSTG/GATEWAY, essentially, the data is sent to TGFTP.nws.noaa.gov as well as
> to the NCF, where the NCF uplinks the data to the SBN/NOAAPORT. UNIDATA and
> other top-tier LDM/IDD sites with an SBN/NOAAPORT ingest system will receive
> METAR data from the SBN/NOAAPORT and inject it into the LDM/IDD network.
> Returning to the NWSTG/GATEWAY, they also send METAR data to other WMO member
> countries at the same time they send the data to TGFTP and NCF.
>
> MADIS is different from the NWSTG/GATEWAY. Note MADIS originated on the
> research side of NOAA (i.e. OAR ESRL/GSD per your weblink) and then a version
> became operational at NWS/NCEP many years ago. MADIS also collected various
> mesonets. From my understanding MADIS is no longer being developed, instead
> the NWS is utilizing [SynopticData](https://synopticdata.com/)to acquire the
> various mesonets. I understand SynopticData also connects with the FAA to
> acquire observational data via a special agreement. You would have to check
> with the FAA (and I'm not sure who it would be) to see if other private
> sector companies connect to the FAA to receive METAR data.
>
> I suspect the lowest latency will be obtaining data from TGFTP, followed by
> an LDM feed from the IDD.
>
> Some weather enthusiasts repurpose old satellite dishes from the 1980s or
> 1990s, originally used for satellite TV, for their own SBN/NOAAPORT satellite
> ingest systems. This includes buying a NOVRA box, computer, etc to ingest the
> data from the dish. This is an option to obtain METAR data from the SBN and
> it would be slightly faster than the latency introduced by the IDD (which is
> likely only a few seconds faster depending on how close your connection is to
> a top-tier site). You could also set up a smaller satellite dish (compared to
> the SBN/NOAAPORT dish) and use the Emergency Managers Weather Information
> Network (EMWIN), which is supposed to include METAR observations. I suspect
> the route of METAR data for EMWIN goes from NWSTG/GATEWAY -> NESDIS -> GOES
> EAST/WEST satellites. Also, I believe there is a terrestrial based EMWIN
> server if you don't want to set up a satellite ingest system.
>
> Gregg
>
> On Tue, Mar 17, 2026 at 10:06 AM Thomas B <thms_brgg@xxxxxxxxx> wrote:
>
>> Hi,
>>
>> Thanks for the pointer to tgftp.nws.noaa.gov — I'm currently polling it and
>> it does seem to be one of the fastest publicly available HTTP sources for
>> METAR.
>>
>> However, from what I've been reading, tgftp serves static files that are
>> regenerated on a cycle (the MADIS documentation at
>> https://madis.ncep.noaa.gov/madis_metar.shtml mentions data is "processed
>> every 5 minutes"). So even with aggressive polling, there's an inherent
>> delay of up to several minutes between the observation time and when it
>> appears on tgftp.
>>
>> By contrast, the LDM/IDD network distributes METAR via push as soon as it's
>> injected from NOAAPort/SBN. The LDM network troubleshooting docs
>> (https://docs.unidata.ucar.edu/ldm/current/troubleshooting/networkTrouble.html)
>> reference sub-second product latency as typical for well-connected IDD
>> nodes.
>>
>> For my use case, that difference matters a lot — I need the lowest possible
>> latency on METAR observations. So I'm really interested in getting an LDM
>> feed rather than polling tgftp.
>>
>> I saw in the FAQ that non-academic users can sometimes arrange a feed from a
>> willing upstream participant.
>>
>> Thanks again for your help.
>> Le lundi 16 mars 2026 à 22:26, Charles Concodora
>> <concodcw@xxxxxxxxxxxxxxxxx> a écrit :
>>
>>> As far as I'm aware, [tgftp.nws.noaa.gov](http://tgftp.nws.noaa.gov/) has
>>> the lowest latency.
>>>
>>>> On Mar 15, 2026, at 2:30 PM, Thomas B <thms_brgg@xxxxxxxxx> wrote:
>>>>
>>>> [tgftp.nws.noaa.gov](http://tgftp.nws.noaa.gov/)
>>
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