Hurricane Isaac hits Louisiana, driving dangerous storm surges

By: Dr. Jeff Masters , 2:27 AM GMT on August 29, 2012

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Hurricane Isaac is ashore over Southeast Louisiana, having officially crossed the coast on the Mississippi Delta 90 miles southeast of New Orleans at 7:45 am EDT on August 28. Isaac intensified right up until landfall, striking with 80 mph winds and a central pressure of 970 mb. The storm's large size and large 50 - 60 mile diameter eye kept the intensification rate slow today, but it came quite close to becoming a significantly more dangerous storm. That's because at landfall, Isaac was in the midst of establishing a small inner eyewall within its large 50-mile diameter eye, a very rare feat I've never seen before. Usually, when an eye first forms, it gradually contracts, eventually becoming so small that it becomes unstable. An outer concentric eyewall then forms around the small inner eyewall, eventually becoming the only eyewall when the inner eyewall collapses. But Isaac is a very unusual storm that has continually surprised us, and this inside-out concentric eyewall formation fits the storm's unusual character. The storm isn't in a hurry to move fully inland, and has slowed down to a crawl this evening. This will give the storm the opportunity to keep its center mostly over water a few more hours, and maintain hurricane strength into the early morning on Wednesday.


Figure 1. Radar reflectivity image from New Orleans as Isaac made landfall at 6 pm CDT August 28, 2012.

A dangerous storm surge event underway
Isaac is bringing large and dangerous storm surge to the coast from Central Louisiana to the Panhandle of Florida. At 10 pm EDT, here were some of the storm surge values being recorded at NOAA tide gauges:

6.2' Waveland, MS
9.9' Shell Beach, LA
3.0' Pensacola, FL
4.4' Pascagoula, MS
3.4' Mobile, AL

The 9.9' storm surge at Shell Beach, which is in Lake Borgne 20 miles southeast of New Orleans, exceeds the 9.5' surge recorded there during Category 2 Hurricane Gustav of 2008. Research scientists running a Doppler on Wheels radar located on top of the 16' levees in Plaquemines Parish near Port Sulphur, LA, reported at 8:30 pm EDT that a storm surge of 14' moved up the Mississippi River, and was just 2' below the levees. Waves on top of the surge were cresting over the west side of the levee. Needless to say, they were very nervous. Over the past hour, the surge has retreated some, and waves were no longer lapping over the top of the levee. This is probably due to the fact that we're headed towards low tide. A storm surge of 9.5' has moved up the Mississippi River to the Carrrollton gauge in New Orleans. This is not a concern for the levees in New Orleans, since the storm surge has now brought the river up to 2.5' above its normal water level, which was 7' low due to the 2012 U.S. drought. The highest rise of the water above ground level will occur Wednesday morning over much of Southeast Louisiana, Mississippi, Alabama, and the western Florida Panhandle, when the tide comes back in. It is clear now that this storm surge event will be as dangerous as that of Category 2 Hurricane Gustav of 2008. One piece of good news: NWS New Orleans successfully launched their 00Z balloon. However, their discussion noted the atmosphere is "saturated or nearly saturated" all the way up to 470mb, or 20,000 feet. Precipitable water was 2.76 inches, which will be ripe for extremely heavy rainfall.


Figure 2. Tide gauge data from Shell Beach, located on the south shore of Lake Borgne, just east of New Orleans. The green line shows the storm surge. The red line is the storm tide, the height of the water above Mean Sea Level (MSL.)

Portlight disaster relief charity responds to Issac
The Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, have mobilized resources in advance of the arrival of Hurricane Isaac. Their crew, including 2 EMTs, is at the Biloxi Special Needs Shelter, and will be caring for shelter dwellers and doing rescues of people who call for help. Another team will be surveying all the shelters in the area to ensure that they are accessible to all people. You can donate to Portlight's disaster relief fund here.

I'll have more in the morning. Hunker down, New Orleans. It's going to be a long night.

Jeff Masters

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1668. LargoFl
Quoting leelee75k:
Just wanted to say thanks to Largo for finding and posting all those pics.
thanks there are lots strating to be posted on the web..trying to find as many as i can so we get an over view of the damage etc..thank my lucky stars this storm didnt not make a righthand turn into Tampa..whew
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Quoting alaina1085:

It's a Hurricane Bromance! ;) hehehe


Pumpkin man meets Kojak and it's love.

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Wow,

Get Real that is amazing...

Everyone stay safe, I'm reeling from the widespread damage Isaac has brought. Speechless as the images & videos come in and it is not over yet. *sigh*
Quoting GetReal:
WOW!!! New record low for my home barometer 28.84 inches!!! I'm located on the southwest side of NOLA metro area, approx 10 miles NNE of Lake Salvador.

Winds still ripping out of the east to ENE...
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pressure 28.74 now
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Quoting mikatnight:


I realize that. I also find Largo's comments to be a welcome addition to the blog.

Just not that one. It sends the wrong message. Very,very wrong.

But, like I always say:

Dying is easy, comedy is hard.


I understand what you're saying now, but I think most thought like me. It might have been better to 'LOL' and then said what you're saying now. And as someone else said, those who hang out on here pretty much know hurricanes and wouldn't do something stupid like that. I did like your info in your post, very good info.
Member Since: August 22, 2009 Posts: 0 Comments: 3151
1662. KEEPEROFTHEGATE (Mod)
Quoting Charliesgirl:
Looks like the eye is ashore, we need it to weaken now.
not too much movement for the next 24 then finally move after that had 6 to 8 inches of rain with another 6 to 8 inches yet too come
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Quoting clwstmchasr:


Take it easy on him Taz. Early models are saying so but as we know things can change.



Ok but I this hate it when evere one looks and the early mode runs and start yelling fish when they no vary well that things wil likey change 100s of times be for they set In done


94L was forecast too be a fish then. Look where it ended up going MX


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Quoting icmoore:


Well, you are a real sweetheart, aren't you!?! I am sorry people but it is not always an easy decision to make to leave your home and this season the models and forecasters have not gotten anything right until it's practically knocking on your door and that does nothing to help. Debby's going to Texas and Isaac was going to be the monster that ate FL...please try not to be so judgemental.


Who's being judgemental? Pot meet Mr. Kettle.

Anyway, the outer Parish's had MANADATORY evacuations. If one stays in a mandatory Evac area., what happens to them is their own fault. i have sympathy for those that were in voluntary evac. areas. However people in mandatory evac. areas are defying the local officials who have their best interests in mind AND stressing the local resources when things go to heck. if you have 20 people stranded on roofs in manadatory evac. areas then you're asking local officials to risk their lives to make up for individual selfishness and stupidity. That's not being judgemental, that's just plain fact.
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Quoting mikatnight:


I realize that. I also find Largo's comments to be a welcome addition to the blog.

Just not that one. It sends the wrong message. Very,very wrong.

But, like I always say:

Dying is easy, comedy is hard.


Now that is good. Fake obviously, but a clever, creative, and very funny pic! :-)
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Quoting vlaming:


How about they will retire it because people in Haiti and the Dominican died?

Then one of those countries would have to come to the WMO meeting and suggest it which Haiti almost never does and the Dominican didn't have anywhere near as many deaths. If Dr.Masters Prediction of 500mil-4bil dollars in damage is correct (or an underestimate) Isaac should be able to retire on damage alone.
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According to the T-P and Nola.com

Hurricane Isaac has knocked out power to more than 450,000 residential and commercial Entergy customers in southeast Louisiana this morning. Entergy's Storm Center website indicated that those included more than 150,000 in Orleans Parish, about 160,000 in Jefferson, some 15,700 in St. Bernard, 10,800 or so in Plaquemines, 27,300 in Lafourche, 16,000 in St. Charles, 16,700 in St. John the Baptist and 17,700 in Terrebonne.
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It's a Hurricane Bromance! ;) hehehe
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1655. ncstorm
Looks like high tide in MS will be around 10:33 am..they will see Isaac 1st real storm surge then..I hope and pray that everyone who is low lying areas evacuated..I believe a lot of people stayed because it was a Cat 1 but didnt realize that Isaac was going to stall..

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Quoting lobdelse81:
Al Roker, what a phony thinking he is a meteorologist, and just a month ago he acted like he was an olympian in London.


aw, heck. He's just doing his job!
Member Since: August 22, 2009 Posts: 0 Comments: 3151
1653. GetReal
WOW!!! New record low for my home barometer 28.84 inches!!! I'm located on the southwest side of NOLA metro area, approx 10 miles NNE of Lake Salvador.

Winds still ripping out of the east to ENE...
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The power looks on and the roads look clear in the eye.

Thanks for the more lively link. 6mph is so SLOW.
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Quoting aislinnpaps:


Largo was just adding humor. She's not drunk or drinking.


I realize that. I also find Largo's comments to be a welcome addition to the blog.

Just not that one. It sends the wrong message. Very,very wrong.

But, like I always say:

Dying is easy, comedy is hard.
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Just wanted to say thanks to Largo for finding and posting all those pics.
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Quoting vlaming:


How about they will retire it because people in Haiti and the Dominican died?
If you're posing that as a moral challenge, sure - that'd be appropriate. As a normative matter? That's not the standard that's been used in the past, and there's been no public change in policy. Many storms, tragically, have inflicted much higher death tolls on Santo Domingo without being retired.
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Quoting icmoore:


Exactly my point it is not an easy decision to make for so many reasons. I have always lived in FL, almost 57 years, but this year I moved to a barrier island and so I have developed a different perspective for sure. There were people who left this area under a past evacuation for Charlie which decided to go inland much earlier than forecast and ended coming back and finding their homes robbed and no bad weather here.


After Rita we had a carload of teens drive down my deadend road with no lights at about 2 in the morning. They parked in the center of the only three houses here and got out, planning on looting. My one neighbor has a relative who is mentally challenged and sleeps whenever he is tired (He has a little one room 'house' on their property). He was up and they scared him so he went into the main house and woke them to say there were people outside in the dark. Those teens were then met with shotguns when they were ten feet from my door and about the same at the other closer house. This is redneck country, you don't mess with them!
Member Since: August 22, 2009 Posts: 0 Comments: 3151
Quoting CloudGatherer:
With Hurricane Isaac still dumping rain, pumping capacity reduced at 17th Street Canal
Published: Wednesday, August 29, 2012, 7:41 AM Updated: Wednesday, August 29, 2012, 7:50 AM
By Rebecca Mowbray, The Times-Picayune
The Army Corps of Engineers says the London Avenue and Orleans outfall canals are fine, but at the 17th Street Canal, the Army Corps was not able start some pumps remotely. Engineers were able to start the pumps manually, but because of the rainfall, the water piled up inside the canal a little higher than the Army Corps would like to see.
The Army Corps is bringing in additional resources to the area, but for now, the Army Corps has had to tell the Sewerage & Water Board to slow down on pumping water into the canal until it can catch up.
Right now, the canal is handling about 70 to 80 percent of capacity.
District Commander Col. Edward Fleming said he plans to call New Orleans Mayor Mitch Landrieu and Marcia St. Martin of the Sewerage & Water Board.

------------------

That's...alarming. To say the least.

Anyone here have a visual on the 17th Street Canal? One report, via Twitter moments ago: "Mom on her way into the city for work she said the 17th street canal looks like its bout to be topped over smh"



its not too alarming, even if it momentalrily tops over it should be held in check
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1646. calder
Quoting Tazmanian:




Poof you go


Why?! (and that question applies to both the 'poofing' and the deeming it necessary to post on the blog)
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Quoting icmoore:


Well, you are a real sweetheart, aren't you!?! I am sorry people but it is not always an easy decision to make to leave your home and this season the models and forecasters have not gotten anything right until it's practically knocking on your door and that does nothing to help. Debby's going to Texas and Isaac was going to be the monster that ate FL...please try not to be so judgemental.


There is a difference if people can't drive/disabled or don't have a car vs people that go out "hurricane partying" before the storm hits and say "it's only a CAT1" or decide the weather is great to go surfing.

The family with the baby (my understanding from a previous post) on their roof d/t flooding is only there d/t their car broke down.
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Quoting AussieStorm:

Geez Taz, take it easy., Even I think 98L will be fish. you going to poof me also.


Just poof Taz... annoying idiot.
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Quoting ncstorm:
according to CNN, over 310,000 customers are without power in LA
According to CNN, the Affordable Care Act was struck down.

According to Entergy, there are currently 451,000 customers without power, and efforts at restoration won't begin until late tomorrow at the earliest.
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1641. vlaming
Quoting CloudGatherer:


I'm not sure the damage alone would justify retirement. But I do think they'll retire the name, if only to avoid confusion.

Isaac is such an extraordinarily strange storm that it's going to be referenced very frequently in the future. People are going to write things like, "Perhaps this storm will form a new eyewall inside of its large and disorganized eyewall, like Isaac," or, "This large and sprawling storm has pressures that are far lower than its associated winds, like Isaac." And that's not to mention the number of research papers and doctoral dissertations for which Isaac has just generously provided data.

No, it'll be retired, even if the 17th Street Canal pumps resume normal operation this morning. The really strange ones almost always are.


How about they will retire it because people in Haiti and the Dominican died?
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Quoting AussieStorm:

Geez Taz, take it easy., Even I think 98L will be fish. you going to poof me also.

We still have September to give us a significant threat with many more waves coming off Africa, and with the pattern we have been in with huge ridging, we better watch out for something.
Member Since: September 9, 2011 Posts: 0 Comments: 435
Quoting all4hurricanes:
I'm just going to guess Isaac will retire.
What an odd storm.


I'm not sure the damage alone would justify retirement. But I do think they'll retire the name, if only to avoid confusion.

Isaac is such an extraordinarily strange storm that it's going to be referenced very frequently in the future. People are going to write things like, "Perhaps this storm will form a new eyewall inside of its large and disorganized eyewall, like Isaac," or, "This large and sprawling storm has pressures that are far lower than its associated winds, like Isaac." And that's not to mention the number of research papers and doctoral dissertations for which Isaac has just generously provided data.

No, it'll be retired, even if the 17th Street Canal pumps resume normal operation this morning. The really strange ones almost always are.
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Quoting Tazmanian:




Poof you go

Geez Taz, take it easy., Even I think 98L will be fish. you going to poof me also.
Member Since: September 30, 2007 Posts: 9 Comments: 15940
Quoting KEEPEROFTHEGATE:
Looks like the eye is ashore, we need it to weaken now.
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1635. MTWX
Quoting ringeaux:


Did you have to Google it to spell it correctly?


Sure did! LOL!!

Actually I Googled rivers in Biloxi, MS, because I didn't even know how to begin spelling it!!
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1634. icmoore
Quoting aislinnpaps:


And remember, not everyone has reliable vehicles, or the money to get a hotel somewhere else. Some won't leave livestock behind, hoping somehow it will work out and not be as bad, some have elderly relations who refuse to leave and they won't leave them there alone. While 'we' want to say, "Why the heck did you stay when you were told to leave?", we're not in their shoes and don't know their circumstances.


Exactly my point it is not an easy decision to make for so many reasons. I have always lived in FL, almost 57 years, but this year I moved to a barrier island and so I have developed a different perspective for sure. There were people who left this area under a past evacuation for Charlie which decided to go inland much earlier than forecast and ended coming back and finding their homes robbed and no bad weather here.
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There is 5 people and 6 dogs in an attic in Braithwaite.
Member Since: September 30, 2007 Posts: 9 Comments: 15940
Quoting Masquer08er:
It's called humor. Most people on the coast know what to do and know when it's safe to have a taste of spirits. This is a weather blog. It's operating room humor. I mean, if you really wanted to be safe, leave town. Then get a motel room and a bottle ;-)
LOL
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1630. ncstorm
according to CNN, over 310,000 customers are without power in LA
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Quoting aislinnpaps:


LOL, neither can I!


Did you have to Google it to spell it correctly?
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Quoting mikatnight:


Prepared to what? Die?

I couldn't disagree more with that statement.

Proper hurricane protocol requires that during a storm one should:

BE

* Calm
* Sober
* Aware
* Decisive

KNOW

* The Storm
* Your Best Defense
* Where to Retreat

HAVE WITH YOU

* Identification
* Water, Nutrition Bars
* First Aid Kit
* Battery Operated Lights
* Battery Operated Radio
* Breakout Tools


It's called humor. Most people on the coast know what to do and know when it's safe to have a taste of spirits. This is a weather blog. It's operating room humor. I mean, if you really wanted to be safe, leave town. Then get a motel room and a bottle ;-)
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Fox 8 News has a man from Braithwaite who house has flooded and claims that the levee there has been topped. He said the water is up to his roof and they are safe but in the attic. He says a deputy friend contacted him early this a.m. advising him of the overtopping. He says his house flooded from nothing to the top of his ceiling in just 5 minutes. The news station has been hearing either a levee topping or levee breach.
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That inner vort showed up again between 05-07Z. I bet there were some much stronger winds associated with it. The statement of being stronger than a CAT 1 may have been true for some.


OLD IMAGE
Member Since: August 19, 2005 Posts: 5 Comments: 5451
Quoting mikatnight:


Prepared to what? Die?

I couldn't disagree more with that statement.

Proper hurricane protocol requires that during a storm one should:

BE

* Calm
* Sober
* Aware
* Decisive

KNOW

* The Storm
* Your Best Defense
* Where to Retreat

HAVE WITH YOU

* Identification
* Water, Nutrition Bars
* First Aid Kit
* Battery Operated Lights
* Battery Operated Radio
* Breakout Tools




Largo was just adding humor. She's not drunk or drinking.
Member Since: August 22, 2009 Posts: 0 Comments: 3151
1624. KEEPEROFTHEGATE (Mod)
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Quoting MTWX:


LOL! I still cant pronounce the name of the Tchoutacabouffa River!!


LOL, neither can I!
Member Since: August 22, 2009 Posts: 0 Comments: 3151
1622. LargoFl
Harrison county..........
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Photo of I-90 in Biloxi, via the Twitter feed of Kim Severson, NYT Atlanta Bureau Chief:
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Quoting all4hurricanes:
I'm just going to guess Isaac will retire.
What an odd storm.
...and it's odd that it hit on the 7-year anniversary of Katrina, almost in the same place!
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Quoting Masquer08er:
my old user name was Say-mo-BEEL. MObil is an oil company or a phone


You could probably get your old name back by requesting the password?
Member Since: August 22, 2009 Posts: 0 Comments: 3151

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.