Tropical storm Isaac intensifies - in pictures

James Cardoza takes a break after helping his boss board up his business in preparation for tropical storm Isaac in New Orleans, Louisiana Photograph: Sean Gardner/Reuters

Motorists make their way out of Belle Chasse ahead of the storm, which is expected to make landfall on the Louisiana coast as a hurricane Photograph: Gerald Herbert/AP

The Industrial Canal levee in New Orleans. The levee wall was rebuilt after hurricane Katrina destroyed it nearly seven years ago Photograph: David J. Phillip/AP

Cecil Lapeyrouse packs his truck with provisions while his wife Dee looks on as they prepare for Isaac's arrival in Cocodrie, Louisiana Photograph: Lee Celano/Reuters

This combination of satellite images shows tropical storm Isaac, top, on 27 August 2012 and Hurricane Katrina on 28 August 2005. Isaac is expected to gain hurricane force by Tuesday and could reach land by Tuesday night or early Wednesday Photograph: Reuters

A house built by Brad Pitt's Make It Right Foundation, helping families rebuild eco-friendly homes in the Lower Ninth ward following hurricane Katrina, stands with covered windows and doors after its occupants evacuated the area Photograph: Skip Bolen/EPA

A worker shovels sand onto a line of fortifications erected in anticipation of Isaac's arrival in Port Sulphur, Louisiana Photograph: Gerald Herbert/AP

A sign gives encouragement to residents in Metairie, Louisiana Photograph: Sean Gardner/Reuters

St Petersburg resident Michael Harper walks as waves crash against the sea wall at Spa Beach in Florida Photograph: James Borchuck/ZUMA Press/Corbis

A protester braves the elements while demonstrating at the Republic national convention in Tampa, Florida Photograph: Tom Pennington/Getty Images

A house raised on stilts sits unoccupied since hurricane Katrina in New Orleans. Louisiana governor Bobby Jindal has declared a state of emergency as the latest forecast shows Isaac moving toward the city Photograph: Skip Bolen/EPA

Another satellite image shows tropical storm Isaac in the Gulf of Mexico. The storm is predicted to strengthen to a category two hurricane before a predicted landfall on the Gulf coast of Mississippi and Louisiana Photograph: NOAA /EPA