This image is in the public domain because it was stored on the web servers of the U.S. National Weather Service. NWS-created images are automatically public domain since the NWS is a part of the US government. However, the NWS sites also host non-NWS images which have been submitted by individuals: these are generally shown as "Courtesy of ...". Such images have explicitly been released to the public domain by the copyright owner as part of the upload process: see for example here, here, here and here.
As stated at http://www.weather.gov/disclaimer.php:"The information on government servers are in the public domain, unless specifically annotated otherwise, and may be used freely by the public....".
Thus, all images on NWS servers are public domain (including "Courtesy of .." images) unless specifically stated otherwise.
To add your language to the list of languages supported by this template, please copy the code of Template:PD-NWS/en (or any other language version you prefer to translate) and replace the text strings in there (the form below can be used to create a translation, the English version is preloaded in the edit box). Please change the parameter lang from en (or whatever language you are translating) to the language code of your language.