"The Big One for the Big Easy" by Mike Naso

[Anonymous]

if a storm came in at the mouth of the Mississippi, it would still likely weaken by about 2 categories before reaching New Orleans, as Betsy did in 1965. Even though its swamp land, a hurricane needs much more water than that to survive.

The storm forecast to make a direct hit on New Orleans in 1995 was Erin, an that would have hit from the east, which means directly into the city. Not only then wouldwe have the surge, but vertical evacuation is then out of the question because we'd have 140 m.p.h. winds as well blowing out all of the upper floors

As for NYC, if a 4 or a 5 were somehow to hit (probably mving NNW so that it doesn't leave the Gulfstream until about 38N), good bye USA. Not sure if our economy would ever recover then as the damage would probably be from 500 billion to 1 trillion (not to mention the damage to NJ, Connecticut, RI, and Mass

Erin in 1995 was forecast to hit New Orleans?

[skysummit]

The massive destruction that had occurred over AL/FL would have PALED in comparison to the damage over SE LA. It would have been SO much worse.

Oh...I highly agree. I don't want to take away from what happened there, but it would've been beyond comparison if a storm of that intensity would hit SE La. We lucked out in more ways than 1 when Andrew made landfall where it did. I had a few gust to 110mph and I was about 40 miles east of the center. We had a little structural damage, but not that much. We also didn't have that much of a storm surge. Areas to our south did though. If Andrew would've taken a track more to the east, it would've been a whole different story.

[Derek Ortt]

a couple of forecasts 18 hours before landfall had it very near NO, but it made an unexpected turn into the Pensacola area

[skysummit]

if a storm came in at the mouth of the Mississippi, it would still likely weaken by about 2 categories before reaching New Orleans, as Betsy did in 1965. Even though its swamp land, a hurricane needs much more water than that to survive.

The storm forecast to make a direct hit on New Orleans in 1995 was Erin, an that would have hit from the east, which means directly into the city.

The difference from due east or southeast really wouldn't make that much difference. If it was coming from due east, it would likely have some sort of affect from hugging the coast of Miss. The water in the marsh areas is not deep at all, but there is plenty of it.

If Camile were to hit today, I wonder what kind of storm surge would come in from Lake Ponchartrain now? I wonder how different it would be. Well....it really wouldn't be considered a "storm surge"....it would just be water getting pushed by northerly winds.

Correct me if I'm wrong, but doesn't storm surge have more to do with pressure, than winds? I asked this last year on Radio NHCWX. Since the pressure is so low in the eye, the water tends to have less "resistance" to rise. I tried to picture it as "less gravity". As the center moves ashore, the rising ocean floor makes that "bubble" of water in the center get higher and higher above the surface and then pounds into the coastline.

Is this correct for the most part?

[x-y-no]

Correct me if I'm wrong, but doesn't storm surge have more to do with pressure, than winds? I asked this last year on Radio NHCWX. Since the pressure is so low in the eye, the water tends to have less "resistance" to rise. I tried to picture it as "less gravity". As the center moves ashore, the rising ocean floor makes that "bubble" of water in the center get higher and higher above the surface and then pounds into the coastline.

Is this correct for the most part?

No. Almost all of storm surge is due to water being driven by wind. There is a smaller pressure related component. Somewhat less than 1cm per millibar, IIRC.

[LaPlaceFF]

A very real possibility.It's not a matter of "if" but "when".

So true....

[Brent]

if a storm came in at the mouth of the Mississippi, it would still likely weaken by about 2 categories before reaching New Orleans, as Betsy did in 1965. Even though its swamp land, a hurricane needs much more water than that to survive.

So how could a 4 or 5 have a direct hit on New Orleans???

[LaPlaceFF]

So how could a 4 or 5 have a direct hit on New Orleans???

I think it's possible..

[Brent]

So how could a 4 or 5 have a direct hit on New Orleans???

I think it's possible..

I think it is too, which is why I asked. He said it would weaken over the swamps which was always the way I thought it would come in. New Orleans isn't oceanfront like Miami.

[Derek Ortt]

Hurricane Andrew only passed over about 15 miles of populated areas in 1992, and spent the rest of its time over the everglades, which are even warmer swamps than LA; however, it weakened significantly over the swamps, likely from 130-135KT down to 115KT and in just a couple of hours.

To survive, there needs to be water down to about 50 feet, not that in the swamps. The weakening wont be as fast as normal land, but still enough. A cane moving from the ESE to the WNW at about 180 would be the worst as it would not hug NS and still make landfall at NO

[Anonymous]

My Erin scenario would keep it a Cat 5 to downtown. If winds coming in are 180, the storm will be still Cat 5 by downtown.

[TS Zack]

Yes, but our marshes are in our backyards. Marshes are also different from swamps. We do have inlets that are that deep. Everything is water/marsh till you hit my area, the Westbank of Jefferson/Plaquemines. The water would be in our homes heading to the second floor by the time this storm made it to New Orleans.

What scares me is watching TS Bill/TS Allison! Do I really want to picture a Cat 3. The new age in New Orleans has not been hit by a Betsy. When Betsy hit there was a heck of alot more marsh than now. I go fishing one weekend, then a month later in the same place, I see how much is lost in that short period of time. It shocks me!

Who remembers when on the way to Grand Isle most of that was Marshes? Now its huge Red Fish Holes.

[MGC]

Dereck, you don't listen do you? We have had this discussion a couple of times now. No way a hurricane will weaken 2 cats when approaching New Orleans from the east. All there is between New Orleans and the GOM is a few miles of marsh. Lake Borne is maybe 5 miles from downtown New Orleans. I challenge you to ask your contacts at the NHC if any of them think a hurricane will weaken 2 cats and I bet you lunch they will say no. Have you ever been to SE La? I've been in the Everglades and the marsh in SE La is nothing like the glades. First off, there are no trees. Only marsh grass about a foot high. Hardly any surface friction. And with the surge the marsh grass will be underwater. You will have the GOM up to the base (or even top) of the levees.....MGC

[tailgater]

My Erin scenario would keep it a Cat 5 to downtown. If winds coming in are 180, the storm will be still Cat 5 by downtown.

If a CAT 5 storm would bear down on N.O. from the east or even east southeast the land friction would greatly reduce the winds in downtown part of town still enough to top lake levees but not the worst case scenario IMHO that would be the same track as Besty moving slow so that it funnel into Lake Borgne then Lake Pontchatrain and Lake Kenner and Lake Metairie.

[drezee]

Change the scenario to early or mid August. Those are indeed the warmest GOM SSTs of the year. By Sep 1st, they are weeks past the peak 25 - 30N in the GOM. Think Camille...

[Derek Ortt]

from the east it wont but the south, it will

if you would read any scientific modeling studies, you would know

[MGC]

I've read the SLOSH studies. How long ago where these studies done? I remember reading them in the 70's when they first came out. In the years since the early studies came out, a whole lot of La coast line has disappeared. Heck, Barataria Bay and Terrebonne Bay have expanded in size. A couple of barrier islands and then marsh for 30 miles. Not much weakening will happen. 2 cats is optimistic from the south......MGC

[Derek Ortt]

newer studies have shown that marsh doesn't really sustain an intense cane, and some research i am about to publish will show that conditions must be extremely favorable or they weaken

[MGC]

Have you a link my good man? Just remember that Andrew kept intensifying while over land in S Fla for a while. The marsh will be covered by 20 feet of surge......MGC

[tallywx]

MGC might have a point with the surge. With Hurricane Andrew, the Everglades didn't experience a surge carried with the storm, whereas the Louisiana marsh would be inundated with tons of water.

Of course, I'm still dubious that a storm could sustain itself on its own storm surge.