Whoever took these pictures did an awesome job.
According to reader Judyb and her link to snopes.com these are not photos of Katrina or any hurricane.
judyb has left a new comment on your post "The Sky Before Katrina Struck - Stunning":
WRONG! The only picture related to Katrina is your next-to-the last photo of the water overflowing the levee in New Orleans East.
The rest of the photos were taking in the summer months of 2002 and 2004 by Storm Chaser Mike Hollingsworth in Nebraska and Kansas. They can be seen at this site
about halfway down the page.
Anyone that has been thru a hurricane knows the skies do not look like tornadoes, as the pictures you posted shows.
Doubt me? Check out snopes dot com on this subject.