I have had a bit of a poke around the CK and after a while found the weather resources, but what looked to be a fairly simple idea is a bit more complex than I suspected (for me at least). I am currently doing quite a number of hours a day getting and testing region settings for Mesogea and doing other 3d stuff etc so have no time to work on sandstorms. As other mods are likely to use them I wondered if anyone with a bit more expertise or with a preference for this kind of thing, might take a look at it and see what can be made in a simple plugin that could then be used as a broader modders resource.
I am region editing the desert so would be in a good position to test it. Is anyone able and willing?
I have done something like that in my old Mod for Oblivion DUNE may be you want to take a look at those effects there but I have no idea if those woudl work in skyrim as well ...
and honestly I do not remember how all that was done I think Midas magic helped me with those ....
http://www.youtube.com/watch?v=DwWDnHHgK6A