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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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?
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Quoting AussieStorm:

Maybe they don't have either of what you have. Makes it easier for them, so what if it takes up a little blog space.


Talked about this yesterday -- people may not have the ability to flip back and forth between pages. Much easier if its on the main blog -- can just run through on smart phones.
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Quoting HurricaneDean07:
>-98L will be the next system to watch... Though it's still located SW of Cape Verde Islands... It has the potential to follow similar to Isaac's footsteps.
If it is named before September 1st, the name would be Leslie, it would be the earliest formation of the 12th Named storm.
Luis formed today in 1995. If it forms by the 31st it would be tied for 2nd along with 2005 Lee and a storm from 1933.
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Quoting weatherh98:


I'm a student at st pauls, do you know how the school is doing?


No, sorry I don't have that information. I have been checking the phones/power at two other homes.. one in Mandeville (about 2 miles from the lake)and one in East Covington and they still have power so I think this area is doing very well so far. Just depends what the storm does next.
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1615. LargoFl
BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE MOBILE AL
751 AM CDT WED AUG 29 2012

THE NATIONAL WEATHER SERVICE IN MOBILE HAS ISSUED A

* TORNADO WARNING FOR...
SOUTHWESTERN GEORGE COUNTY IN SOUTHEAST MISSISSIPPI...
SOUTHERN PERRY COUNTY IN SOUTHEAST MISSISSIPPI...
NORTHEASTERN STONE COUNTY IN SOUTHEAST MISSISSIPPI...

* UNTIL 830 AM CDT

* AT 747 AM CDT...A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A
TORNADO WAS LOCATED 15 MILES NORTHWEST OF ESCATAWPA...OR 6 MILES
NORTHWEST OF WADE...MOVING NORTHWEST AT 45 MPH.

* LOCATIONS IMPACTED INCLUDE...
RURAL SOUTHWESTERN GEORGE COUNTY
RURAL SOUTHERN PERRY COUNTY
RURAL NORTHEASTERN STONE COUNTY

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A TORNADO WATCH REMAINS IN EFFECT UNTIL 400 PM CDT WEDNESDAY
AFTERNOON FOR SOUTHWEST ALABAMA AND SOUTHEAST MISSISSIPPI.
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I'm just going to guess Isaac will retire.
What an odd storm.
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Quoting LargoFl:
this lady says I am ok, im prepared..........


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


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1612. IMA
"WDSU reporter Gina Swanson said water was encroaching on an evacuation shelter in Raceland, in Lafourche Parish."
from wdsu.com
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1611. LargoFl
Weeks bay.................
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Quoting aislinnpaps:


My son was telling a relative from NY he had decided to go to school at NSU. About thirty minutes minutes later they called back and asked for me saying they couldn't find any Nack-a-dish on any map.
my old user name was Say-mo-BEEL. MObil is an oil company or a phone
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-Isaac will be a big problem for the Gulf coast for the Next 36 Hours... Then He will turn into a blessing for drought stricken states further north.
-Kirk will be a system to run up the numbers and will probably be very similar to Gordon.
-98L will be the next system to watch... Though it's still located SW of Cape Verde Islands... It has the potential to follow similar to Isaac's footsteps.
If it is named before September 1st, the name would be Leslie, it would be the earliest formation of the 12th Named storm.
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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"
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1607. MTWX
Quoting aislinnpaps:


We do have some fun names for people from not around here or not familiar with French!


LOL! I still cant pronounce the name of the Tchoutacabouffa River!!
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Kirk looks like he is trying to organize.

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1605. LargoFl
8/29/2012. PLAQUEMINES PARISH - Officials report extensive damage in Plaquemines Parish in southeast Louisiana,
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1604. FOREX
Quoting Tazmanian:


Looks like a Fish Storm.
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Quoting LargoFl:
this lady says I am ok, im prepared..........


YOU WILL SURVIVE NOW

THREE HAZZAAASS

HAZAAA HAZAAA HAZAAA
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Quoting LargoFl:
this lady says I am ok, im prepared..........
You should send that to Absolut. Very good!!!
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Quoting SELouisianaGirl:
In north Covington, LA. Rain is light with wind gusts and has been all night. Waiting to see what other wobbles Isaac has in store so we can find out what the next 24 hrs hold. Local weather people thinks it gets worse in our area over the next 12 hours and through tomorrow but if Isaac move more to the west that might not happen. Power still on.



I'm a student at st pauls, do you know how the school is doing?
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Quoting Masquer08er:
Yeah Stephanie on TWC tried to say Bayou Gauche. At least she admitted she wasn't sure how to say it. Yesterday someone said DOE-fin Island. We don't make it easy on them.


My son was telling a relative from NY he had decided to go to school at NSU. About thirty minutes minutes later they called back and asked for me saying they couldn't find any Nack-a-dish on any map.
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Quoting WxNerdVA:
Oh wow, the NHC has Kirk as a hurricane now!

Looks like it is heading straight for NOLA! LOL
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In north Covington, LA. Rain is light with wind gusts and has been all night. Waiting to see what other wobbles Isaac has in store so we can find out what the next 24 hrs hold. Local weather people thinks it gets worse in our area over the next 12 hours and through tomorrow but if Isaac move more to the west that might not happen. Power still on.

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still way too early too tell


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1595. LargoFl
this lady says I am ok, im prepared..........
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Quoting GetReal:
Well I guess that my post in reference to the coastal erosion and more open water to the south and Se of NOLA panned out. Isaac took advantage of those now open waters the past 16 hours to maintain strength, and get better organized.


He would have weakened if those islands and marshes were still there.
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The GFS track et al have just been posted for 8AM. It looks like St. Lucia will be OK.
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29/1200 UTC 17.8N 112.1W T4.0/4.0 ILEANA -- East Pacific
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Quoting GeorgiaStormz:
We are just about at high tide, so peak flooding should occur now.



It will be tomorrow at high Tide in my location
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Have lost power. Lucky I had it so long.
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1589. Jay5711
Quoting LATHUNDERBOLT:


more gusty than earlier for sure - wind a little east of north - 1 very brief sprinkle around 3ish that was just enough to get things wet - already dried


Rain just started here but light rain, expecting power to go out sometime today, as it usually goes out with a thunderstorm. hopefully rain will stay to east, but the way it moving I expecting the eyewall to pass over us later today
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Quoting aislinnpaps:


We do have some fun names for people from not around here or not familiar with French!
Yeah Stephanie on TWC tried to say Bayou Gauche. At least she admitted she wasn't sure how to say it. Yesterday someone said DOE-fin Island. We don't make it easy on them.
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Water coming up on the northshore
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We are just about at high tide, so peak flooding should occur now.

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1585. calder
Quoting hurricanehunter27:
Kirk is supposed to become a Cat 1 now according to the NHC. Weird trend for sure.


Interesting trend indeed, hurricanes telling TS's to get back in the kitchen to make dinner! Think nea noticed this yesterday
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1584. LargoFl
fishing pier at Biloxi
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Live cam and broadcast in east side of new orleans.

Link
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1582. ncstorm
Quoting LargoFl:
HWY90 Biloxi miss


Look like Mississippi is having the worst of the flooding problems..
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Quoting hurricanehunter27:
Kirk is supposed to become a Cat 1 now according to the NHC. Weird trend for sure.
At first it was only supposed to be a minimal TS.
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This is what the UK Guardian paper is saying about a levee breach. Not sure if it means they're expecting it to fail or just stating worst case scenario.



"Floodwater has already lapped over an 18-mile (29km) stretch of the levee along the Mississippi river in Plaquemines Parish, south-east of the city, threatening serious flooding. Billy Nungesser, the president of the coastal Plaquemines Parish, said the 3-metre levees had not yet collapsed, but warned that roads in the area were already impassable, hindering the evacuation of the few remaining residents.

"As that water flows over the top, it eventually will eat out portions of that levee, which then it washes away. Either that or the inside of the levee will fill up. One or the other will happen. Either way that area's going to be totally inundated with water," he told CNN."
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Quoting AussieStorm:

It's better to give than receive.



yep
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1578. calder
The people that downplay the situation here clearly haven't been through a hurricane before (or are just idiotic!). Can't imagine what would've happened if Isaac had stalled as a cat 3/4, there would've been devastation.

To those affected - good luck, be safe, drink whisky (notice this is the correct spelling :)) and keep posting! You are making my day at work slightly less tedious.

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Quoting SWLACajun:
Thanks Taz. Given the unusual movements and actions of Isaac, which model has been more on track?



i think the gfs gets the gold and the ecw gets sliver
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Quoting Tazmanian:



what about the B storm?

Beryl. Womans name.
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1575. LargoFl
HWY90 Biloxi miss
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Quoting ncstorm:
Good Morning..

Issac is making his mark on the gulf states. My prayers are with everyone down there.
Im in Lake Charles, we are to the west, of course watching, been reading blog for a week, nice to know you are there.
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Quoting Tazmanian:



so ture

It's better to give than receive.
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1572. ncstorm
the president of one of the parrish said this morning that he has more destruction of his home from Isaac than he did with Katrina..he said he had a wall knocked out..hole in his roof..he ended it saying this was not a category 1 hurricane..
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Thanks Taz. Given the unusual movements and actions of Isaac, which model has been more on track?
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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.


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.
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Quoting hurricanehunter27:
I have to ask does anyone have rain totals from Isaac so far?


2.48

Pressure 990.5
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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