Hurricane Irene vs. Hurricane Katrina: How They Stack Up

As Hurricane Irene was bearing down on the East Coast late last week, many commentators warned of its destructive potential by invoking the memory of Hurricane Katrina.

Hurricane Katrina slammed into the Gulf Coast six years ago today (Aug. 29), flooding nearly all of New Orleans in the process. The storm remains a potent cultural touchstone, serving as a reminder of nature's power — and the importance of planning properly for worst-case scenarios.

Since Irene made landfall and was downgraded to a tropical storm over the weekend, we can begin to take its measure a little better. So how does Irene compare to Katrina?

Birth date and place

Irene: Meteorologists gave Irene its name Aug. 20. At that point, it was a tropical storm about 190 miles (306 kilometers) east of the Caribbean island of Dominica. In the early hours of Aug. 22, Irene graduated, becoming the first hurricane of the 2011 Atlantic season.

Katrina: Katrina was named Aug. 24, 2005, when it was a tropical storm about 65 miles (105 km) east-southeast of Nassau in the Bahamas. Katrina became the fifth hurricane of the 2005 Atlantic season when it was upgraded the next day.

Storm path

Irene: Irene made landfall in Puerto Rico in the early morning of Aug. 22, then continued to move northwest. As it neared the U.S. East Coast, Irene banked heavily north, churning toward another landfall in North Carolina.

The storm came aground at that state's Cape Lookout around 7:30 a.m. EDT Saturday (Aug. 28). Irene then kept moving northward in near-shore waters, hitting New York City around 9 a.m. EDT Sunday (Aug. 28) and New England a few hours later.

Katrina: Katrina took a completely different route. The hurricane made landfall in southeast Florida on Aug. 25, then popped out into the Gulf of Mexico to the west. It churned westward through the Gulf for a while, gaining strength from the warm waters, then arced northward.

Katrina made its Gulf landfall on the morning of Aug. 29 near Buras, La., about 50 miles (80 km) southeast of New Orleans. The storm kept weakening as it moved north, finally dying out around the Great Lakes region Aug. 31. [In Photos: Gulf Coast Damage from Hurricane Katrina]

Size

Irene: Irene's mammoth size made many forecasters nervous, as the storm had the potential to pummel huge swaths of the Eastern Seaboard with heavy rain, flooding and strong winds. At its largest, Irene measured about 600 miles (966 km) across, nearly as big as Texas.

Katrina: The 2005 storm was also enormous, though apparently not quite as big as Irene. Katrina was about 400 miles (644 km) wide when it made landfall in Louisiana.

For what it's worth, the biggest hurricane ever recorded was Typhoon Tip. (Hurricanes in the western Pacific Ocean are called typhoons.) The 1979 storm, which made landfall in southern Japan, was nearly 1,400 miles (2,253 km) wide at one point. That's almost half the size of the continental United States. [Hurricanes from Above: See Nature's Biggest Storms]

Intensity

Irene: Irene was a big, bad storm, but it could have been worse. The hurricane maxed out at Category 3, meaning its highest sustained wind speeds never topped 130 mph (209 kph). And Irene was not that powerful when it hit populated areas.

Irene was still just a tropical storm, for example, when it passed over Puerto Rico. It was a Category 1 hurricane when it hit North Carolina, with maximum sustained wind speeds around 85 mph (137 kph). By the time it hit the Northeast, Irene had weakened to a tropical storm again, with top winds of about 60 mph (97 kph).

Katrina: While Hurricane Irene covered more area, Katrina was more intense. In the Gulf of Mexico, Katrina grew into a Category 5 hurricane — the strongest storm there is. Katrina's maximum sustained winds reached speeds of around 173 mph (278 kph).

But Katrina weakened as well before making landfall. When it hit Louisiana, the storm had been downgraded to a Category 3 hurricane and boasted max wind speeds around 127 mph (204 kph).

Death and destruction

Irene: While it's far too early to fully gauge Irene's impact, it's already clear the storm is far from another Katrina.

Irene's storm surge likely maxed out around 4 to 8 feet (1.2 to 2.4 meters) along the East Coast, and it drenched huge swaths of land with heavy rain. As a result, many areas have suffered serious flooding, meaning Irene's economic toll will be considerable. Some experts say it is likely to be the 10th of the billion-dollar weather disasters of 2011.

However, the destruction is nowhere near that of Katrina's. As of Sunday morning, news reports pegged Irene's cumulative death toll at 10 or so — not even close to the human toll Katrina exacted.

Katrina: Katrina was an epic disaster. The hurricane flattened and flooded much of coastal Alabama, Mississippi and Louisiana, generating storm surges of nearly 28 feet (8.5 meters) in some places.

Some experts estimate Katrina caused $125 billion in damage, making it the costliest natural disaster in U.S. history. And the storm killed more than 1,800 people, the vast majority of them in Louisiana. Many of these people died after New Orleans' levee system failed and most of the city was flooded.

Getting out of the way

Irene: In general, most East Coast communities took Irene very seriously and started taking measures early. New York Mayor Michael Bloomberg, for example, issued a mandatory evacuation order for low-lying areas of the city at 2 p.m. EDT Friday (Aug. 26), nearly 48 hours before the hurricane hit the Big Apple.

Other population centers along the coast were similarly cautious, and millions of people were told with plenty of time to spare to get out of Irene's path.

Katrina: New Orleans Mayor Ray Nagin issued a voluntary evacuation order on the evening of Aug. 27, 2005. As the storm bore down on his city, the mayor upped that to a mandatory order around 11 a.m. the next day — about 18 hours before the storm hit.

The vast majority of New Orleans residents got out of harm's way. But some who were less mobile — seniors, disabled people and those without cars, for example — were left behind, and many of them died. Six years later, who should bear the brunt of blame for this evacuation failure is still being debated.

This SPACE.com story was provided by OurAmazingPlanet, a sister site to LiveScience. You can follow Mike Wall, senior writer for SPACE.com, on Twitter: @michaeldwall.