Thomas,
I do have to say that this sounds very much like a prediction market
request; I've received over 20 of these in the last six months. I have 3
from the last 24 hours in my inbox, all sounding eerily similar to this.
EMWIN requires a satellite dish. The FTP is for archive purposes and is the
same as the TGFTP endpoint. https://www.weather.gov/emwin/
You'll likely receive better answers to your Synoptic Data questions by
asking them directly.
On Wed, Mar 18, 2026 at 9:29 AM Thomas B <thms_brgg@xxxxxxxxx> wrote:
> 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 has the lowest latency.
>>
>> On Mar 15, 2026, at 2:30 PM, Thomas B <thms_brgg@xxxxxxxxx> wrote:
>>
>> tgftp.nws.noaa.gov
>>
>>
>>
>> _________________________________________________________
>> NOTE: All exchanges posted to NSF Unidata maintained email lists are
>> made publicly available through the web. Users who post to any of the
>> lists we maintain are reminded to remove any personal information that
>> they do not want to be made public.
>>
>> NSF Unidata ldm-users Mailing List
>> (ldm-users@xxxxxxxxxxxxxxxx)
>> For list information, to unsubscribe, or change your membership options,
>> visit: https://mailinglists.unidata.ucar.edu/listinfo/ldm-users/
>>
>
>
> --
> **********************
> *========================================================================*
>
>
>
> *Email seems to be generating increasing inefficiencies in organizations.
> I learned from a manager a Stanford Computer Science professor no longer
> uses email for communication, but uses SNAIL mail, telephone calls, and
> person to person visits. I'm considering the same. 405-325-2462*
>
> *Storm Prediction Center*
>
> *120 David L. Boren Blvd, Suite 2330Norman, OK 73072*
>
>
> _________________________________________________________
> NOTE: All exchanges posted to NSF Unidata maintained email lists are
> made publicly available through the web. Users who post to any of the
> lists we maintain are reminded to remove any personal information that
> they do not want to be made public.
>
> NSF Unidata ldm-users Mailing List
> (ldm-users@xxxxxxxxxxxxxxxx)
> For list information, to unsubscribe, or change your membership options,
> visit: https://mailinglists.unidata.ucar.edu/listinfo/ldm-users/
>