This storm is so powerful and growing more powerful every day that I'm not sure we've seen anything like it.-New Orleans mayor Ray Nagin
NVDL: It is the wee hours of the morning in the USA, and Gustav has justed cleared Cuba. It is now a Category 3 storm, but it has all day to power up again. The fact that it sustained Cat 4 throughout the night is in itself significant.
It is almost three years to the day since Hurricane Katrina swept through the birthplace of jazz, killing hundreds and exposing deep poverty and lack of preparation.
Highways around New Orleans are jammed and hundreds of people having been lining up to board buses as authorities urge residents to get out before the storm gets any closer.
Sky News weather presenter Lucy Verasamy said: "This hurricane won't just affect New Orleans - but that city still hasn't recovered from Katrina and the levees will never be able to take Gustav's storm surge of over 20ft. No way."
After passing over Cuba, Gustav lost some power and dropped to Category 3 - but the fierce storm is now back over the warm Gulf waters where it will pick up strength again, possibly reaching a catastrophic Category 5.
Energy companies have shut down three-quarters of oil production in the Gulf and are prepared for the strongest storm in three years to hit an area that produces a quarter of US crude and 15% of its natural gas.