Take a look at other subs and flesh it out more. Take peoples advise on spellchecking.
If you need a word processor, check out OpenOffice (Google it). It's free and it works well.
You're the author - the mage's name need not be lost to history. I've suggested before that one can have the Players History which can be vague, incomplete and wrong, and then the GM's history which provides the GM what he needs to know about the item. Go to Comment
Personally, I like powerful items (to a degree) and a one shot hurricane item does not bother me, so long as it was dang expensive and difficult to create.
It could easily cause an "Oh Crap!" moment :)
I would have it take effect over a slightly longer period then 30 seconds. To affect miles and miles of clouds, the magic effect would need to take a while.
What if there were no clouds? I could see them appearing, but 30 seconds?
Now, this really is the equivalent to a magic Atomic Bomb and would need to be treated as such with attendant magical protections, security forces, etc.
An enemy mage could easily teleport (if available) into a city, plant and activate it, and then leave. Go to Comment