The National Weather Service (NWS) has released experimental radar imagery which takes advantage of Google Earth 4′s new time animation feature to show animated data. This means you can see the last hour’s worth of radar images animated over Google Earth. Right now, you have to select which city you want to see (hopefully they will add a map interface to make the selection process easier). To use this (you must have the latest Google Earth 4 installed), go to the new experimental NWS RIDGE Loops in KML page, and choose the location in the US you are interested in viewing from the drop down menu. I selected “Louisiana->New Orleans” in the example shown. Then I selected “Composite Reflectivity“. Click on “Submit” and you will get a KML file loaded in Google Earth. The time slider gadget should appear in the upper center of GE’s main window. Make the slider range real big to load all the images, then make the gadget smaller. Next, select the “Play” button (a little right arrown/triangle on the right edge of the time gadget). This will animate the radar for you. You can also click and drag the middle of the slider back and forth.
The NWS released a wider range of KML files for radar and other data (without the animation feature) on this page a few months ago. They also have supported a very nice US-wide radar and warning guide by the Severe Storms Lab. Check it out the US-wide radar example here (be patient, it’s a fairly large overlay).
Thanks to Tim at the NWS for telling me about the new service. Also mentioned at OgleEarth.