August 29, 2005 6:10AM: Katrina reaches Bay St. Louis, Mississippi as a Category 3 hurricane, resulting in one of the most devastating natural disasters ever on U.S soil. At $135 billion in damage, it stands as the costliest hurricane in United States history and with 1,836 lost lives, ranks among the top five deadliest. As we look back at this 10 year anniversary, we examine the storm’s influence in the meteorological community and learn that Katrina inspired vast improvements not only in hurricane forecast accuracy but also in communication of forecasts to the general public.
Right from the start, Katrina was an overachiever and rapidly intensified into a massive Category 5 hurricane in a matter of days. In its inital stage, Tropical Depression Twelve formed over the Bahamas on August 23, 2005 and soon grew to Tropical Storm Katrina on the 24th. The storm wasted no time becoming a Category 1 hurricane on the 25th, shortly before making its first landfall in South Florida. After pressing through Florida, Katrina entered the Gulf of Mexico, where warm sea surface temperatures from the Gulf Loop Current enabled Katrina to explode into an incredibly large Category 5 hurricane with sustained winds of 175 mph. As it headed towards the Mississippi and Louisiana Gulf shores on the 29th, Katrina encountered cooler waters. Albeit weakening, it remained a strong and very large Category 3 hurricane, spanning 400 miles in diameter with sustained winds of 125mph.
On August 29, 2005, Katrina barreled into coastal Louisiana and Mississippi as the third strongest hurricane (based on surface pressure) to ever make landfall in the United States (behind only Hurricane Camille in 1969 and the 1935 Labor Day hurricane). The animation above shows Katrina’s landfall during which the strongest winds were in the northeastern quadrant of the storm. These winds piled record setting storm surge onto the vulnerable Gulf Coast with the surge peaking at 28 feet in Bay St. Louis, Mississippi. The stress from this historic surge led to the infamous levee breech in New Orleans, located 50 miles west, submerging 80% of the city in more than 10 feet of water. As Katrina pushed further inland, it weakened and eventually dissipated by the 31st.
On a more positive note, the meteorological community can credit Katrina for its inspiration towards advancements in weather satellites and improved hurricane forecast accuracy. One such inspiration came from Katrina’s rapid intensification over the warm Gulf waters. Since bouy data is limited in the Gulf and Atlantic waters, scientists rely on satellites to determine water temperatures. Katrina enlightened meteorologists to the importance of sea surface heights, a satellite product that enables them to determine the heat content of water. Knowing where warm water lies informs meteorologist as to where tropical systems will strengthen. To learn more information about favorable and unfavorable conditions for hurricanes, see our blog.
Another major improvement to hurricane forecasts is expected to come from the launch of a new satellite fleet called GOES-R in 2016. Updated images of tropical systems will be available every 30 seconds which will reflect important features of a developing hurricane sooner. For comparison, the GOES-12 satellite during Katrina updated images only every 5 minutes. Considering how quickly Katrina strengthened, meteorologists have learned every second counts. Even hurricane hunter aircraft have seen advancements with the launch of the Coyote unmanned aircraft. Meteorologists can now retrieve valuable data from parts of hurricanes that manned aircrafts cannot travel to safely.
Additionally, there has been a new emphasis on the public issuance of hurricane forecasts. The Saffir-Simpson scale, the official ranking system of the National Hurricane Center that categorizes hurricanes, has been simplified since Katrina. It now only considers wind conditions and has a new heightened focus on storm surge with storm surge watches and warnings currently under testing. Finally, a greater emphasis has been placed on more detailed calls for action, enabling the public to further understand the impact of a weather forecast rather than just the forecast itself.
