It is in fact a fact that the area was a rain forest at one time, it was about 10,000 - 12,000 years ago....
the wind currents changed and dried the area out..
10,000-12,000 years ago? Well that is EVEN before the Egyptian civilization.
There is nowhere on the Internet that says that. You must have read that in a book. [A WHAT?!?!--oh yeah, a book! :o)]
"Wind currents" wouldn't have dried up an area that large anyway. I believe your book had some other place in mind. That area has been desert forever.