I took a screen grab of the satellite images of Gustav as it nears the Louisiana coast. Man it’s huge. If you use Google Earth’s measurement tool, it is about 1,000km by 900km in size. The green is the radar signal.
In this picture I measured the circumference of the main part of the storm, it came at over 3,000km.
On this picture you can see the distance between the two red marks, it’s almost 1,000km.
And here it is without the labels…