The National Oceanic and Atmospheric Administration forms assessment teams to study the forecasts and recommend improvements after major weather disasters.
The Weather Service's National Hurricane Center projected more than two days in advance that Katrina would strike southeast Louisiana as a major hurricane and later issued hurricane watches and warnings with lead times of 44 and 32 hours, the report said. That's an extra eight hours beyond when such alerts are typically issued.
"The accurate forecasts provided for extended warning times," said Weather Service Director David L. Johnson. "Our ability to identify where a major hurricane would hit the Gulf Coast was among the actions that saved countless lives."
Katrina first crossed Florida on Aug. 25, made its second landfall in Buras, La., on Aug. 29 and them moved on to the area near the border of Louisiana and Mississippi.
The storm devastated coastal areas, flooded much of New Orleans and forced evacuation of thousands of people.
The Weather Service reported 1,353 direct fatalities from the storm and 275,000 homes damaged or destroyed and said total economic losses could top $100 billion.
The storm created "extremely challenging" working conditions for the Weather Service, the report observed, particularly in disrupting communications, which limited its ability to send out warnings. Weather Service offices from Florida to Texas were called on to provide backup services.
Noteworthy, the report said, was a warning issued by the New Orleans office a day before the storm's arrival emphasizing the probable impacts and reinforcing the need for evacuation.
The assessment called on the agency to study likely points of communications failure in the event of similar storms and to find ways to improve continuing operations, including providing hardware and software needed for extended periods of service backup.