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 angiest:


It was even a bit breezy in Katy when we left home this morning.


Getting a little breezy in Jefferson County.



Partly Cloudy and Breezy

83°F

28°C

Humidity67%
Wind SpeedN 22 G 31 mph
Barometer29.65 in (1004.1 mb)
Dewpoint71°F (22°C)
Visibility10.00 mi
Heat Index88°F (31°C)
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2118. LargoFl
Quoting 12george1:

Yes, Palm Beach County has been largely ignored
yes im afraid the bigger picture takes hold today..we are thinking about you folks though..stay safe down there as well ok
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Quoting dader:


In this country, we suffer fools all too gladly. They need to be billed for rescue and then they will leave. Too many "tough guys/gals" who want to ride it out below sea level.

that area is not below sea level - on the natural banks of Mississippi river.
Member Since: Posts: Comments:
2116. angiest
Quoting LargoFl:
Just think..most or all of those houses with water up to their roof tops are going to have to be condemmed and bull dozed..the mold will shortly become a very real health danger....just wondering..does that area have gators?


Is there a part of southern Louisiana that doesn't?
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Looks like Isaac has pulled up a beach chair and is enjoying the coastline...not in a hurry to leave.
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Quoting CybrTeddy:
If we close out August with 12 named before peak season, unless September really turns out to be a bust, finding it difficult to see how 2012 will end up with less than 15 named storms at this rate. Not any major hurricanes yet though, rather surprising lack of those.


I´m QUITE SURE 98L(Leslie) will be our first major hurricane..especially if recurve
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Looks like the Orleans Avenue Canal is about to overtop at Pumping Station 7, near I-610

http://www2.mvr.usace.army.mil/WaterControl/shefg raph-wotem2.cfm?sid=85642&d=7&dt=S
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Quoting LargoFl:
Just a note..Palm beach county florida, is going thru one of those ..once in a 100 year floods, Isaac affected so many area's along the gulf coast huh..a tragedy really

Yes, Palm Beach County has been largely ignored
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Quoting jpsb:
I am American but 7 of my 8 grand parents are Scots. And I love Scotch Whiskey, must be in the genes.


is that McCallahan (not sure if I'm spelling that right) Scotch? My dad drinks that stuff on the rocks. He gave me and my brother each a glass of it one Christmas Eve while sitting around a campfire. When he walked away, we both threw it in the fire. It was AWFUL! We felt bad because we knew it was expensive, but man oh man was it terrible. LOL! To each his own, I guess.
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2110. LargoFl
Just think..most or all of those houses with water up to their roof tops are going to have to be condemmed and bull dozed..the mold will shortly become a very real health danger....just wondering..does that area have gators?
Member Since: Posts: Comments:
That's what I said about second guessing (about 6 p.m. yesterday). Some of those folks might have left had NHC declared a hurricane yesterday morning but maybe not. The mayor in Plaquemines declared on NPR that 'this was no CAT 1!'
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2108. Skyepony (Mod)
Waveland surge is pushing 10' now.
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2107. dader
Quoting Jstn568:
SO frustrating seeing the reports of all the rescues in Plaquemines Parish come in. So many people did not leave when there was a mandatory evacuation ordered. I think they thought, "oh it's a TS/Cat 1, no big deal." And now look. There's a lesson here, one that seems to be taught over and over because people get too complacent. Granted, I know that some people can't leave for various reasons, but so many didn't even try.

Alright, stepping down from the soap box before the flood waters wash it away.


In this country, we suffer fools all too gladly. They need to be billed for rescue and then they will leave. Too many "tough guys/gals" who want to ride it out below sea level.
Member Since: Posts: Comments:
Quoting Jstn568:
SO frustrating seeing the reports of all the rescues in Plaquemines Parish come in. So many people did not leave when there was a mandatory evacuation ordered. I think they thought, "oh it's a TS/Cat 1, no big deal." And now look. There's a lesson here, one that seems to be taught over and over because people get too complacent. Granted, I know that some people can't leave for various reasons, but so many didn't even try.

Alright, stepping down from the soap box before the flood waters wash it away.



Somehow they manage to leave when the rescue boat gets there..... just sayin
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Any news about how the potentially explosive, radioactive sinkhole is holding up with the eye right over it?

Found the two items below but that's it.

http://www.examiner.com/article/sinkhole-parish-w ide-evacuation-no-cots-assistance-checks-or-rescue
http://www.examiner.com/article/isaac-50-miles-fr om-sinkhole-trees-down-people-stranded-on-rooftops
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2104. angiest
Quoting Skyepony:


From my estimate he has moved just over 80nm miles from his first landfall on the delta, some 16 hours ago.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting Grothar:


This is getting very bad. Prayers being sent.

sheri
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2102. LargoFl
Just a note..Palm beach county florida, is going thru one of those ..once in a 100 year floods, Isaac affected so many area's along the gulf coast huh..a tragedy really
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2101. Jstn568
SO frustrating seeing the reports of all the rescues in Plaquemines Parish come in. So many people did not leave when there was a mandatory evacuation ordered. I think they thought, "oh it's a TS/Cat 1, no big deal." And now look. There's a lesson here, one that seems to be taught over and over because people get too complacent. Granted, I know that some people can't leave for various reasons, but so many didn't even try.

Alright, stepping down from the soap box before the flood waters wash it away.
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Quoting MoldyinMS:


True, pets are a big part of it. In my experiences, relatives with alzhiemers or maybe mentally challenged in some other way that would not do well anywhere but home. So many reasons besides losing stuff. That was the point I was making. You can replace stuff, if you have the resources.

I'm not elderly yet but I live on a barrier island (in Florida) and would stay because of pets and also because my mother refuses to go anywhere and she lives across the street. Not moving a 55 gallon fish tank, either.
Member Since: Posts: Comments:
2099. jpsb
Quoting RitaEvac:


WIND ADVISORY IN EFFECT
UNTIL 8 PM CDT THIS EVENING
Urgent - Weather Message
National Weather Service Houston/Galveston TX
1037 AM CDT Wed Aug 29 2012

... Wind Advisory In Effect Until 8 PM CDT This Evening For
Galveston Chambers Counties...

.Increasing Winds Will Occur Today Due To The Interaction Between
High Pressure Over Western Texas And Hurricane Isaac Over
Southeastern Louisiana. Winds Will Increase This Morning To
Between 20 And 30 Mph And Possibly Gust To 35 Mph This Afternoon.
The Winds Are Expected To Gradually Diminish Tonight And Thursday.

Chambers-Galveston-
Including The Cities Of... Anahuac... Friendswood... Galveston...
League City... Mont Belvieu... Texas City... Winnie
1037 AM CDT Wed Aug 29 2012

Starting to see traffic in the Ship Channel now, guess all danger to Texas from Issac is gone. Great!
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Quoting RitaEvac:
from coming of Africa....In the end....this storm went WELL WEST, look where he is




And this is almost identical of what models were calling for on Isaac when he was out there. Expect this future storm to plow well west in the end too folks, get ready.



hmm we think alike


Quoting HopquickSteve:
Is that a hole, or is Kirk's CoC actually forming an eye?


could be and could be a dry spot these storms this year tend to have that

Quoting 7544:
list below
isaac
kirk
98L
possibly 99L off of africa now

what a active augest and the the peak is sept 10 ?
will these other system get close enough to make a run for the us landfalls still? maybe we going to see a couple of home brewed ? and has the mojo arrived yet thanks stay safe


so far I think we are just at the tip of the iecberg here
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2096. Skyepony (Mod)
Compare that radar loop to the one Jeff left up top. Hasn't moved much in the last 17hrs...

Houma in the eye..
Member Since: Posts: Comments:
2095. angiest
Quoting RitaEvac:


WIND ADVISORY IN EFFECT
UNTIL 8 PM CDT THIS EVENING
Urgent - Weather Message
National Weather Service Houston/Galveston TX
1037 AM CDT Wed Aug 29 2012

... Wind Advisory In Effect Until 8 PM CDT This Evening For
Galveston Chambers Counties...

.Increasing Winds Will Occur Today Due To The Interaction Between
High Pressure Over Western Texas And Hurricane Isaac Over
Southeastern Louisiana. Winds Will Increase This Morning To
Between 20 And 30 Mph And Possibly Gust To 35 Mph This Afternoon.
The Winds Are Expected To Gradually Diminish Tonight And Thursday.

Chambers-Galveston-
Including The Cities Of... Anahuac... Friendswood... Galveston...
League City... Mont Belvieu... Texas City... Winnie
1037 AM CDT Wed Aug 29 2012



It was even a bit breezy in Katy when we left home this morning.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
2094. Skyepony (Mod)
Member Since: Posts: Comments:
Quoting DVSmith:


Arthur, Bertha and Fran all came ashore at Cape Fear in 1996 (I was living on Oak Island at the time).

Arthur was a TS, Bertha a Cat 1, which had stalled off SC and weakened from a Cat 2, before zipping up the eastern part of the state. Fran slammed ashore as a strong Cat 3 and was still a decent Cat 2 when it went through Durham.

Bonnie, in 1998, made landfall at Cape Fear as a Cat 3 and barely moved, dropping down to a TS, before curving back out to sea as a weak Cat 1 (having strengthened over the sounds).


Georges in '98 stalled over us for 3 days, slowly blowing himself out. Came into Pascagoula/Biloxi area and stalled on the beaches, putting Mobile on the dirty side, and slowly drifted eastward right across us. We had hurricane-force winds in Mobile for quite a long time.
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Quoting TxGrandma:
Okay, I admit it....I saved a copy of Pat's puppy picture because I wanted to show it to my SO when he got home and was afraid I wouldn't be able to find it again. Would I be breaching WU blog protocol to repost it (assuming I can figure out how)?


Ha, I saved it, too. But I'm a huge dog dork.

I see a bunch of us posted links. They're all super famous now, hope it doesn't go to their heads. :D
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2091. Eagle84
LOPL1 is STILL under storm-force winds and gusts at or over 80 knots. Except for the few hours spent under the COC it's been experiencing those conditions for about 36 hours straight.

Member Since: Posts: Comments:
2090. kwgirl
Quoting AussieStorm:

I'm a teddy bear man. if you know what that means you'll know where my family comes from.
I only got to Inverness once about 16 years ago. Beautiful as is all of Scotland.
Member Since: Posts: Comments:
People on top of houses in the mandatory evac zone, I guess some people have thick heads. I constantly hear "I want to be home to protect my property" - STUPID!! Now county and city officials have to be put in harms way for rescues. How can you protect property from your rooftop? DUMB!!
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2088. Relix
Quoting wunderkidcayman:

hey Relix right, (I'm not wishcasting ok). I don't buy the track going NW and recure out to sea. them same models that's forecasting 98L, did Isaac and when Isaac was an Invest(94L) models were in almost the same place as they are now for 98L, well maybe just a bit N of what 98L models show, and well we sure saw what that invest 94L turned out to be, mean old Isaac. so as I said and someone else said it, we will have to wait a bit longer.

also 98L is about 1 whole degree S of where Isaac was when he was an invest


This time I don't buy it. It*may* go N of the Islands but definitely not that curve upwards.
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2087. Grothar
Member Since: Posts: Comments:
If we close out August with 12 named before peak season, unless September really turns out to be a bust, finding it difficult to see how 2012 will end up with less than 15 named storms at this rate. Not any major hurricanes yet though, rather surprising lack of those. Though to be honest, it's not often you see 11-12 named before September so it's not a huge shock that there hasn't been a major hurricane yet. 1988, 1989, 1997, 2001, 2002, and 2006 all didn't see a major hurricane until September.
Member Since: July 8, 2005 Posts: 259 Comments: 23574
2085. SirCane
Quoting Thing342:
Interesting photo of Kirk. He's definitely trying to organize.



Looks like a peewee compared to Isaac...
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Quoting duprk452:
Just getting on this a.m. This thing is just sitting on top of us in Terrebonne Parish. The news is focusing on New Orleans, so can anyone tell me what to expect this storm to do?

Do ya'll still have power? Stay safe!
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Quoting jpsb:
Wind is dying down here in San Leon, was blowing 20-25 (mph) on the bay now 12-18. Guess Issac is losing steam.


WIND ADVISORY IN EFFECT
UNTIL 8 PM CDT THIS EVENING
Urgent - Weather Message
National Weather Service Houston/Galveston TX
1037 AM CDT Wed Aug 29 2012

... Wind Advisory In Effect Until 8 PM CDT This Evening For
Galveston Chambers Counties...

.Increasing Winds Will Occur Today Due To The Interaction Between
High Pressure Over Western Texas And Hurricane Isaac Over
Southeastern Louisiana. Winds Will Increase This Morning To
Between 20 And 30 Mph And Possibly Gust To 35 Mph This Afternoon.
The Winds Are Expected To Gradually Diminish Tonight And Thursday.

Chambers-Galveston-
Including The Cities Of... Anahuac... Friendswood... Galveston...
League City... Mont Belvieu... Texas City... Winnie
1037 AM CDT Wed Aug 29 2012

Member Since: Posts: Comments:
Quoting weatherh98:


It's one in the same

I read it with an accent to:)


I read everyone's posts as James Earl Jones and Morgan Freeman saying them together.

Except for Reedzone, he sounds like Gilbert Gottfried.
Member Since: Posts: Comments:
Quoting TxGrandma:
Okay, I admit it....I saved a copy of Pat's puppy picture because I wanted to show it to my SO when he got home and was afraid I wouldn't be able to find it again. Would I be breaching WU blog protocol to repost it (assuming I can figure out how)?
Fine by me if you repost...seems like lots haven't seen it..back to lurking...
Member Since: Posts: Comments:
2080. dader
Quoting AussieStorm:
75 rescued in Plaquemines Parish - 25 still stranded



Goodnight for real now.


Wasn't there a mandatory evacuation order for Plaquemines. The people who stayed should be billed for rescue services.
Member Since: Posts: Comments:
Quoting Relix:
any takes on 98L? Have an event here in PR on Sunday and want to see if that recurve seems more likely than not.

hey Relix right, (I'm not wishcasting ok). I don't buy the track going NW and recure out to sea. them same models that's forecasting 98L, did Isaac and when Isaac was an Invest(94L) models were in almost the same place as they are now for 98L, well maybe just a bit N of what 98L models show, and well we sure saw what that invest 94L turned out to be, mean old Isaac. so as I said and someone else said it, we will have to wait a bit longer.

also 98L is about 1 whole degree S of where Isaac was when he was an invest
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Quoting duprk452:
Just getting on this a.m. This thing is just sitting on top of us in Terrebonne Parish. The news is focusing on New Orleans, so can anyone tell me what to expect this storm to do?


Here is the last NHC Forecast Discussion from 2 hours ago

FORECAST POSITIONS AND MAX WINDS

INIT 29/1500Z 29.6N 90.7W 65 KT 75 MPH...INLAND
12H 30/0000Z 30.2N 91.4W 55 KT 65 MPH...INLAND
24H 30/1200Z 31.2N 92.2W 45 KT 50 MPH...INLAND
36H 31/0000Z 32.8N 93.1W 30 KT 35 MPH...INLAND
48H 31/1200Z 34.6N 93.5W 25 KT 30 MPH...INLAND
72H 01/1200Z 38.0N 92.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 02/1200Z 40.0N 89.0W 15 KT 15 MPH...POST-TROP/REMNT LOW
120H 03/1200Z 41.0N 85.0W 15 KT 15 MPH...POST-TROP/REMNT LOW

Member Since: Posts: Comments:
Quoting kwgirl:
Ach aye. My wee bairn is Scots by birth. Dunoon, Argyll, Scotland, UK. If you went into a bar and asked about the Scottish people, you would be buying a round, its Scots.


I'm well familiar with Dunoon, and the general area of Holy Loch. Spent a year there as a child.
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75 rescued in Plaquemines Parish - 25 still stranded



Goodnight for real now.
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Quoting dogsgomoo:
There's a picture of puppies?!


This is the only one I saw, born right as the bands were really starting to pound:

link

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Quoting dogsgomoo:
There's a picture of puppies?!
Okay, I admit it....I saved a copy of Pat's puppy picture because I wanted to show it to my SO when he got home and was afraid I wouldn't be able to find it again. Would I be breaching WU blog protocol to repost it (assuming I can figure out how)?
Member Since: Posts: Comments:
2073. jpsb
Quoting Pirate999:
For our Houstonians...

Ananometer at 68' (on a sailboat mast) in Seabrook. Winds consistent 18kt from 340 with gusts to 25kts. Water dropping in the bay. Oh, and HOT.
Wind is dying down here in San Leon, was blowing 20-25 (mph) on the bay now 12-18. Guess Issac is losing steam.
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Quoting Giga2001:
Can anyone give me a general idea of the status in NOLA? Specifically the areas of Algiers Point, the area near the Maple Leaf Bar (Uptown/Carrolton) and St Charles Ave around the 1700 block?



Live News Coverage in NOLA

Link
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Quoting duprk452:
Just getting on this a.m. This thing is just sitting on top of us in Terrebonne Parish. The news is focusing on New Orleans, so can anyone tell me what to expect this storm to do?
It's going to be there for quite some time. And if you haven't gone through the eastern eyewall yet, it's going to be rough for several hours.
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Quoting duprk452:
Just getting on this a.m. This thing is just sitting on top of us in Terrebonne Parish. The news is focusing on New Orleans, so can anyone tell me what to expect this storm to do?


You're in the eye. You have more rain and wind coming
Member Since: June 17, 2011 Posts: 11 Comments: 6461
2069. jpsb
Quoting wunderkidcayman:

oh really Aussie because I'm also part Scottish myself
I am American but 7 of my 8 grand parents are Scots. And I love Scotch Whiskey, must be in the genes.
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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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