I have used rtupdate.wunderground.com for rapid-fire updates from a MeteoBridge for a couple of years now. Over the last day I experienced all kinds of problems and once I did a network trace I noticed that virtually all requests to this server get connected, but never receive a reply and eventually time out. Every now and then a request seems to get through.
So it seems yet another problem with wunderground.com
Workaround: Use
www.wunderground.com instead. This seems to work fine, even for rapid-fire updates.
Additional benefit: It appears rtupdate, even when uploading every 15 seconds, only gives you back data once every 5 minutes in the graph and tabular data. When using
www.wunderground.com today I actually get graph and table data once a minute!