They COULD have been spun off by an approaching hurricane...
...but these look more like air-mass thunderstorms and super-cells, typical of the american midwest.
They're still cool photos, even if not Katrina related.
I've been in the path of, or in the vicinity of, several approaching hurricanes. In my experience most of the destructive thunderstorm activity is found embedded in the storm, and would not loan itself to photos like these.
The air around the hurricane is generally subsiding (sinking) and so would not have the lifting action to form storms like these clear of the hurricane itself.
For instance, here is Hurricane Jeanne off my left wing last year:
More photos of my Hurricane Jeanne return flight at: