Katrina formed in a broad area of low pressure in the southeast Bahamas on August 23. A combination of satellite estimates and aircraft reconnaissance caused Katrina to be upgraded to a tropical storm the following day. Katrina moved westward through the Bahamas as it was steered by a subtropical ridge to its north. Despite battling dry air intrusion and some northerly shear, Katrina strengthened into a hurricane on August 25.
It made its first landfall as a Category 1 hurricane on August 25 near Hallandale, Florida causing approximately $600 million dollars in insured damage ($1.2 billion dollars in total damage). Estimated winds at the system’s first landfall were near 70 knots. Katrina weakened briefly to a tropical storm as it traversed the southern part of Florida, but it then restrengthened into a hurricane once it reached the Gulf of Mexico.
Once it entered the Gulf, it encountered an area of low vertical wind shear and very warm sea surface temperatures, including traveling over the very warm waters of the Gulf loop current. It intensified into a major hurricane on August 27 while traveling underneath a very strong upper level anticyclone. Late on August 27, Katrina began rapid intensification due to continued low vertical wind shear and very warm sea surface temperatures.
It was upgraded to a Category 5 hurricane during the morning on August 28. During the afternoon of August 28, Katrina’s central pressure dropped to 902 mb which made it the fourth lowest pressure ever recorded in the Atlantic at that time. Katrina weakened to a Category 4 hurricane late on August 28 due to a combination of dry air intrusion and an eyewall replacement cycle. However, the system maintained Category 4 intensity until making landfall near Buras-Triumph, Louisiana on August 29 with estimated winds of 125 knots.
It made a second landfall near Waveland, Mississippi as a Category 3 hurricane with estimated winds of 110 knots. The system weakened once it made its final landfall, and the final advisory was written on the system on August 30 while it was traveling northward through Tennessee.
Katrina became the most damaging and destructive hurricane on record in the United States with estimates of insured damage currently at approximately $50 billion dollars ($100 billion dollars total damage). New Orleans was devastated by the storm with about 80% of the city flooded after storm surge breached several of the levees in the city, and most property along the western Mississippi coastline was either damaged or destroyed. The current death toll from the system is 1302.
Summary courtesy of William M. Gray and Philip J. Klotzbach
18 November 2005
