08.29.12

Could Isaac Be Worse Than Katrina For Parts Of Northern Gulf?

Posted in Commentary, Storm History, Storm Facts, Hurricane Intensity, Tracking the Tropics at 11:06 pm by gmachos

Storm Shows That It’s Not Your Typical Category One Hurricane

At first glance one wouldn’t think that Isaac is worth comparing to Hurricane Katrina. With its tremendous size, significantly lower pressure, and higher wind speeds and seas, Katrina was able to devastate the Northern Gulf coast like no other storm to a region of the United States. It was the deadliest U.S. hurricane since 1928, and the costliest natural disaster in the country’s history. The storm is among the top six strongest on record in terms of pressure.

Then, there is the images from the suffering in New Orleans following the storm. People standing on roof tops, pleading for help in front of the Convention Center, the state of anarchy that existed throughout the Big Easy, and the mass exodus from the city in the days and weeks after the storm. With all of this to consider when comparing Katrina to Hurricane Isaac, one would think that it would be a no brainer. However, with some thought and closer inspection, people may have a different idea. There are several things to keep in mind when looking back on Katrina. The path of the storm, decrease in intensity just prior to landfall, and short duration prevented this historic storm from being even worse.

Exactly several years ago to the day (Imagine the irony of that!), Hurricane Katrina took a path that put it to the east of New Orleans, which put the Crescent City on the weaker western side of the storm. Some people forget that it was the Mississippi Gulf Coast that bore the brunt of Katrina’s vicious right front quadrant. New Orleans only had winds of 90 miles per hour, and there were initial thoughts that the Big Easy had withstood the blow from the storm. It was only after the levee system had failed and the flooding began in the Lower Ninth Ward that a catastrophe was unleashed. This time around, Isaac traveled along a path that took it to the west of New Orleans and much of Southeastern Louisiana took the brunt of the right front quadrant.

Consequently, there was more of a storm surge factor for places such as Plaquemines Parish, which may have suffered worse flooding from Isaac than Katrina. Levees were breeched in a couple locations, and residents that stayed behind were caught by surprise after thinking the storm wasn’t going to be as bad. Another factor that may make Isaac worse than Katrina in some respects is its duration. Due to its very slow forward motion, Isaac is doing two things: 1.) Dumping tremendous amounts of rain over a long period of time, and 2.) Bringing in more and more surge and that is putting pressure on the levee system, especially in Plaquemines and St. Bernard’s Parishes. Many of these levees stand outside the area fortified by the Army Corps of Engineers in the wake of Katrina.

Issac is also not your typical Category One storm. The hurricane only had winds of minimal hurricane force at 80 miles per hour. However, around the times of its two landfalls, Isaac had a minimum central pressure that dropped to 968 millibars, or 28.58 inches of Hg, which was a pressure more typical of a solid Category Two Hurricane on the Saffir-Simpson Scale. Combined with the large size of the storm, the pressure gave the storm energy that took a long time to wind down because of the vast expanse of it. Throw in the slow forward speed, and you had a relentless storm that pounded the coastline of the Northern Gulf. Over 24 hours after landfall, Isaac was still generating storm surge of 6 to 7 feet in some places.

The slow motion of Isaac is also helping to bring tremendous amounts of rain to Louisiana and Mississippi. Rainfall amounts are ready in the area of a foot or more in some places, and could end up between 20 and 30 inches. Meanwhile, Katrina was a relatively fast mover. The massive storm was out of the area within 24 hours. Isaac is expected to linger around Louisiana for another day after pounding it for about 30 hours now. One thing that could help prevent more substantial flooding from Isaac is the fact that the Mississippi is at very low levels due to the drought throughout much of the Midwestern portion of the country. The Mighty Mississippi was at more normal levels at the time of Katrina.

Hurricane Katrina will forever be embedded in our minds thanks to the power and fury its winds and surge possess as well as the heartbreaking images from its aftermath. However, for some along the Northern Gulf coast such as Plaquemines Parish in Louisiana, Hurricane Isaac will be remembered as the little train that could, and was more devastating.

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