This has been requested many times, and it came down to the fact it would be too laggy. The only way to make a proper tornado would be to make it out of emitters, which would slow down the server badly. There was an idea to have one large .gif image, but that wouldn't work very well either.
.gif would probably work because, it won't need allot of server juice.. and a good .gif of a tornado can be done.
but too get a more realistic affect on the bricks, the image would need to be sliced into sections, to allow different widths.
I like this idea... I can already picture this, dark clouds hovering over my crapy fort and destroying it, and than 30 seconds later it's brand new.. LOL
I guess admin can use this instead of clearing bricks..