Meltemi, Harmattan, Chinook, Freemantle, Sirocco...
Nokia's been using winds as codenames for years. Volkswagen also discovered them recently too (Sirocco, Passat, Bora), and let's not forget the well-travelled "Ghibli" - used by Maserati, but before that, the WW2 Italian aircraft maker Caproni, whence the renowned filmmaker Hayao Miyazaki adopted it as the name for his animation studio.
On the topic, this is good news. The problem with MeeGo was that it was a "Linux distro" for mobiles (and other platforms, I know). This meant that there were many ways to write applications and services - a native widget set, and also Qt, and a browser for web apps too, and myriad installable packages that you had to support... a lot of complexity that needs to be maintained at every release. This is what is killing Symbian - the need to maintain compatibility with APIs that are well past their sell-by date.
Series40 has been successful because it exposes only one API to developers: J2ME. Underneath, the "Domestic OS" is free to change to adapt to new hardware... it might even be a Linux kernel (but I don't think it is).
Similarly, I expect that Qt/Meltemi will be Linux-based, but it won't be a Linux like Debian or Fedora, or even MeeGo: there would be no "native UI toolkit" exposed. Istead, *all* application development will be via the Qt APIs, and the exact mapping of these features to OS functions will be free for Nokia to play with as they see fit. (Again, my guess) only the core functions of Linux, like the POSIX libraries and things like sockets, will be available.
Using Linux greatly speeds up base-porting; using Qt greatly improves applications' resistance to a change of the underlying OS.
For a parallel, think of MacOS/iOS - they're BSD underneath, but almost none of the applications are written to the BSD APIs.
If you consider that what smartphones do today, featurephones will do in two years, then there's a major explosion in mobile applications coming...