August 29th: Remembering Two Major Hurricanes to Hit the U.S.

August 29th is the anniversary of the most notorious and costliest hurricane in U.S. history, Katrina, but also Hurricane Ida 16 years later in 2021. Both made landfall along the Gulf Coast, devastating communities in Louisiana and Mississippi with storm surge and flooding.  

Katrina 

On Wednesday August 24, 2005 tropical depression 12 strengthened into tropical storm Katrina and hit the Florida Keys as a CAT 1 Hurricane on Thursday. During its 6 hours in the sunshine state, Katrina left $600M in damage and was responsible for 14 deaths.  

Katrina then reemerged into the Gulf, weakened from time over land as a tropical storm. But that didn’t last long, by Saturday Katrina was a MAJOR hurricane, a powerful CAT 3 and then rapidly intensified into a CAT 5 with winds of 175 mph.  

Just before landfall Katrina weakened to a CAT 3 with sustained winds of 125 mph. The rapid weakening was likely due to an eyewall replacement cycle just ahead of landfall. The first landfall was in SE Louisiana before a second landfall along the Mississippi Gulf Coast.  

Despite weakening, Katrina’s shear size created huge waves and wide reaching impacts. Just offshore from southern Alabama a wave of 55’ was measured as Katrina came ashore. 

The storm surge from where Katrina made landfall was nearly impossible to determine due to the damage, but it is estimated to have been 24 to 28 ft along the Mississippi coast across a swath about 20 miles wide, centered around Bay St. Louis.  

The city of New Orleans was evacuated the day before Katrina hit and many people could not get out in time, and the “Superdome” became a shelter for nearly 20,000 people. Officials weren’t ready for the influx of people – they only brought supplies for 15k people for 3 days.  

The levees in the city of New Orleans were breached by a surge of 15-19 feet, leaving 80% of the city underwater. Over 10 feet of water covered St. Bernard Parish, covering rooftops. In the lower ninth ward 6 to 8 feet of water stranded people in their homes. Winds gusted up to 100 mph in the city.  

Sadly, over 2,000 people lost their lives during Hurricane Katrina and its aftermath. Katrina is the third deadliest hurricane in U.S. History, after the 1900 Galveston Hurricane and 1928 Lake Okeechobee Hurricane. It remains the costliest natural disaster in U.S. History – producing $193.8B in damages (2023 cost adjusted).  

Ida 

The first landfall of Ida was in Port Fourchon, Louisiana at 11:55 AM CDT on August 29th. Winds were sustained at 150 mph and pressure was down to 930 mb. Ida tied Hurricane Laura from the previous year for the strongest storm on record to hit the state.  

The second landfall occurred at 2:00 PM CST near Galliano, Louisiana as a category 4 storm with sustained winds of 145 mph and pressure of 934 mb. 

24 tornadoes touched down in Gulf Coast states and into the South as Ida was under tropical characterization. 34 people in Gulf Coast states lost their lives because of Ida, most in post-storm fatalities of heat exhaustion and CO2 poisoning from generators.  

After devastating the gulf coast, Ida then traveled north through the Appalachians, eventually becoming post tropical over West Virginia on September 1st. Despite the downgrade in status, Ida brought deadly flash flooding and damaging tornadoes along the I-95 corridor from Maryland to New England.  

An EF-2 tornado touched down near Annapolis and there were 7 confirmed tornadoes in Eastern Pennsylvania & New Jersey. An EF-3 was on the ground for more than 12 miles in Mullica Hill, NJ, the strongest in the state in 31 years.  

More widespread than the tornadoes was the flooding – made worse by previous tropical systems Henri and Fred which saturated the soils in the Northeast.  

Flash flooding on the night of September 1st turned streets around the NYC metro into rivers – 4 separate flash flood emergencies were issued by the NWS as basement apartments flooded and subway systems. Sadly, 49 people lost their lives in the Northeast as a result of Ida, 48 as a result of flooding. 

Ida was the costliest disaster of 2021, with over $60B in damages.