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.

The levee failures prompted corps commander Lt. Gen. Carl Strock to commission an investigation of the New Orleans flood protection system. In New Orleans, responsibility for the system's design and construction belongs by the federal statute to the Corps of Engineers. Other congressional investigations were launched into response of the federal, state and local governments, resulting in the resignation of Federal Emergency Management Agency director Michael D. Brown. Conversely, the National Hurricane Center and National Weather Service were widely commended for accurate forecasts and abundant lead time. Three years later, thousands of displaced residents in Mississippi and Louisiana were still living in trailers.

Meteorological history

main: Meteorological history of Hurricane Katrina

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.

The storm rapidly intensified after entering the Gulf, growing from a Category 3 hurricane to a Category 5 hurricane in just nine hours. This rapid growth was due to the storm's movement over the "unusually warm" waters of the Loop Current, which increased wind speeds. On Saturday, August 27, the storm reached Category 3 intensity on the Saffir-Simpson Hurricane Scale, becoming the third major hurricane of the season. An eyewall replacement cycle disrupted the intensification, but caused the storm to nearly double in size. Katrina again rapidly intensified, attaining Category 5 status on the morning of August 28 and reached its peak strength at 1:00 p.m. CDT that day, with maximum sustained winds of 175 mph (280 km/h) and a minimum central pressure of 902 mbar. The pressure measurement made Katrina the fourth most intense Atlantic hurricane on record at the time, only to be surpassed by Hurricanes Rita and Wilma later in the season; it was also the strongest hurricane ever recorded in the Gulf of Mexico at the time (a record also later broken by Rita).

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.