One note about Ham Stations too is that depending on what else they might be doing on APRS (which is where our weather data goes too, as well as some CWOP data, depending on how the operator is sending it to the network) they might use their callsign, or callsign-x (where x is a number 1-15). My weather station for example is K5GHS-1 because I run a APRS application on my home computer that is using my callsign sans any number. (I might have to change this, I'm waiting to hear back from NWS, if so, I'll have to swap it and my weather station). But I have seen other hams use a -x identifier for their weather station. This is the reason why other identifiers are used too (I was an ASxxx in California before I wasn't able to upload to CWOP with my old station, just got back into it, but thats one of a few identifiers a station may have). Most ham stations nowadays use internet to get their data to the NWS, but some still do it the old fashioned way-transmitting it out as a APRS packet via RF, to hopefully be picked up by a relay that will "repeat" it to a APRS station that is connected to the internet (Igate). This happens especially for stations that may have slow or unreliable internet, or remotely located stations that can reach another APRS station to relay it, or just people who have a radio license, so they want to send it in via radio, period. Those go out on APRS first then into the network via the nearest IGate. I won't get more technical than that, but if you look at the packets on Findu, you'll see TCPIP if they came in via internet without any radio relay. Otherwise you'll see the callsign path they took via RF to get to the internet.
The only thing that this affects is whatever site or software you're using may not identify -x stations right, so you may not be seeing some Ham Radio related WS if they only look for the callsign minus the identifier.
I actually use quite a few different identifiers. Depending on my physical location, and what devices or radios I have turned on at the time, there could be as many as SIX identifiers clustered on my house. Even when I'm not home there will be a few there, namely the main if my APRS map is running, my weather station now on -1, my phone using APRSDroid, as well as my tablet on that as well (this is where anyone who sends me a message via APRS sends them to) as well as my vehicle (this is actually a "pure RF" APRS, that transmits my location as I move, used to track me when I'm storm chasing, which is what the map I have at home is for, you can watch the weather and direct people AWAY from the main storm track-we're out there to gather data, not toss a trailer into a storm a-la "Twister."). I also have a handheld radio that will transmit APRS, though that one has to be really close to a relay to get into the APRS network because of its low signal.
If you look up APRS there is a ton of data on it, but depending on the map you look at, you might see a WX icon for a Ham operated Weather Station, but if its also showing you APRS data, you'll see other devices too. That is what they are, either internet based trackers, or RF trackers on handhelds or Mobiles. At times they even do balloon launches and put an APRS trackers in them too. Usually storm chasers turn off ambiguity (the ability to mask the precise location a bit) when chasing, because if a storm is moving fast, they want Skywarn Net Control to be able to direct them out of harms way, or tell them to get under cover before a hail core hits, etc. Some operators even send out APRS data showing what radio they are operating, wattage being used and stuff like that. Many times if there is a local "Hamfest" or event they will put an icon for it on APRS somehow. There are some people with setups in their cars with dedicated small screens they use just to look at APRS data. I'm not that deep into it but it does exist, and some people use it to send messages instead of the internet, like in the old "packet radio" days with 1200 baud RF modems....
FindU will list all of the associated trackers, etc having to do with a callsign. Just do a search for the call without any -x and it will list all of them. I believe you can have 16 total (the callsign alone, then -1 to -15). Some people do use all of them for various purposes.
http://www.aprs.org/aprs11/SSIDs.txt shows a list of what the are usually used for-however this isn't always followed, and if you have an "established" SSID for whatever reason, changing it might require notifying quite a few people (which is why I'm hoping I can leave mine alone at home, but if it has to be sans ssid for the weather station I'll change it).
This won't affect most of what you're looking for, and I believe probably nowadays most sites might use the "AS" ID versus the callsign for data, but if they are just looking by callsign, they are probably missing a lot of WX stations without one. If you know a ham radio operator nearby and can't find their weather station by callsign, do the generic search on FindU and you'll probably find it under a SSID.
The APRS system is a real interesting system and there are still a lot of people using it today, and a lot of weather stations using it to get their data into the network. "Bah! I will always send my reports by radio. Using the internet is cheating!" ...some operators do think this, for sure.
Just one other way that data flows into CWOP, at least on the Amateur Radio side.
EDIT: Typos
