Hurricane Katrina of the 2005 Atlantic hurricane season was the costliest hurricane, as well as one of the five deadliest, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall.
At least 1,836 people lost their lives in the actual hurricane and in the subsequent floods, making it the deadliest U.S. hurricane since the 1928 Okeechobee hurricane. Economist and crisis consultant Randall Bell wrote: "Hurricane Katrina in 2005 was the largest natural disaster in the history of the United States. Preliminary damage estimates were well in excess of $100 billion, eclipsing many times the damage wrought by Hurricane Andrew in 1992."
Four years later, thousands of displaced residents in Mississippi and Louisiana were still living in trailers. Reconstruction of each section of the southern portion of Louisiana has been addressed in the Army Corps LACPR Final Technical Report which identifies areas not to be rebuilt and areas and buildings that need to be elevated.
Hurricane Katrina formed as Tropical Depression Twelve over the southeastern Bahamas on August 23, 2005 as the result of an interaction of a tropical wave and the remains of Tropical Depression Ten. The system was upgraded to tropical storm status on the morning of August 24 and at this point, the storm was given the name Katrina. The tropical storm continued to move towards Florida, and became a hurricane only two hours before it made landfall between Hallandale Beach and Aventura, Florida on the morning of August 25. The storm weakened over land, but it regained hurricane status about one hour after entering the Gulf of Mexico.
Katrina made its second landfall at 6:10 a.m. CDT on Monday, August 29 as a Category 3 hurricane with sustained winds of 125 mph (205 km/h) near Buras-Triumph, Louisiana. At landfall, hurricane-force winds extended outward 120 miles (190 km) from the center and the storm's central pressure was 920 mbar. After moving over southeastern Louisiana and Breton Sound, it made its third landfall near the Louisiana/Mississippi border with 120 mph (195 km/h) sustained winds, still at Category 3 intensity.
On the morning of Friday, August 26, at 10 a.m. CDT (1500 UTC), Katrina had strengthened to a Category 3 storm in the Gulf of Mexico. Later that afternoon, the NHC realized that Katrina had yet to make the turn toward the Florida Panhandle and ended up revising the predicted track of the storm from the panhandle to the Mississippi coast. The NHC issued a hurricane watch for southeastern Louisiana, including the New Orleans area at 10 a.m. CDT Saturday, August 27. That afternoon the NHC extended the watch to cover the Mississippi and Alabama coastlines as well as the Louisiana coast to Intracoastal City.
President of the United States George W. Bush declared a state of emergency in selected regions of Louisiana, Alabama, and Mississippi on Saturday, the 27th, two days before the hurricane made landfall. That same evening, the NHC upgraded the storm alert status from hurricane watch to hurricane warning over the stretch of coastline between Morgan City, Louisiana to the Alabama-Florida border, 12 hours after the watch alert had been issued, and also issued a tropical storm warning for the westernmost Florida Panhandle.