I posted this previously, but now the radar data from Hurricane City also comes directly from NOAA. Previously the radar data went through my site first and then to Hurricane City, which relied on my site to be operational. Now Hurricane City is an independent backup if my site goes down.
I created a rapidly updating radar product for Google Earth:
http://hurricanecity.com/recon/recon.cgi?live_radar=1Hurricane City checks for data every 5 minutes and lately radar scans are available on NOAA's server about two minutes after being taken, so that should update very quickly. (The site will increasingly check less often the longer radar data has not come in.)
It usually updates very quickly after data is available. It checks for data when the NOAA hurricane hunters are doing recon. Other than determining if data needs to be downloaded, the download of data is separate from the rest of the recon system, where radar data is more delayed as it takes time to determine where it should be placed along a flight path.
Also, there is an ArcGIS map here that will always be at least 30 minutes delayed:
http://hurricanecity.com/recon/live_radar/arcgis_map/ArcGIS has that delay for Google Earth KML files. Eventually I'll get around to other options, like Google Maps. Hopefully later this year.
All of this is subject to error. I'm still working out bugs.