Isaac pounding Louisiana, Mississippi, Alabama, and Florida

By: Dr. Jeff Masters , 4:01 PM GMT on August 29, 2012

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Hurricane Isaac continues to lumber slowly northwestwards at 6 mph, as it pounds Louisiana, Mississippi, Alabama, and Florida's Panhandle with torrential rains, high winds, and a damaging storm surge. The eye was partially over water for most of the 15 hours after Isaac's official landfall at 7:45 pm EDT Tuesday night, but New Orleans radar shows the eye of the storm is now fully ashore near Houma. The radar echoes show some weakening on the west side of the eyewall, where dry air has infiltrated the storm. Wind shear remains light, and upper level outflow over Isaac is as impressive as we've seen so far, with a strong outflow channel to the north, and a respectable one to the south, as well. Infrared and visible satellite loops show a very large, symmetric, and well organized storm, and Isaac is going to be able to stay near Category 1 hurricane strength all day today. This will allow Isaac to drop rainfall amounts of 15 - 20" in some areas of Louisiana before the storm is over. A few rainfall totals from Isaac through 11 am EDT:

9.26" New Orleans Lakefront Airport
5.59" Belle Chasse, LA
5.21" Mobile, AL
3.65" Hattiesburg, MS
3.42" Gulfport, MS
2.81" Biloxi, MS


Figure 1. Morning radar reflectivity image from New Orleans.

A dangerous storm surge event underway
Isaac is bringing a large and dangerous storm surge to the coast from Central Louisiana to the Panhandle of Florida. Late this morning was high tide along much of the coast, and the highest water levels of Isaac are likely being experienced at many locations. At 11:30 am EDT, here were some of the storm surge values being recorded at NOAA tide gauges:

8.0' Waveland, MS
8.2' Shell Beach, LA
2.0' Pensacola, FL
4.6' Pascagoula, MS
3.4' Mobile, AL

The peak 11.06' storm surge at 1:30 am EDT this morning at Shell Beach, which is in Lake Borgne, 20 miles southeast of New Orleans, exceeded the 9.5' surge recorded there during Category 2 Hurricane Gustav of 2008. In general, the storm surge heights from Isaac have been more characteristic of a strong Category 2 hurricane, rather than the weak Category 1 hurricane one might suppose Isaac is, based on its top sustained winds of 75 - 80 mph. The Saffir-Simpson Scale for ranking hurricanes is only a crude measure of their potential impacts.

A storm surge estimated at 12' moved up the Mississippi in Plaquemines Parish near Port Sulphur, LA, near 8:30 pm EDT Tuesday, causing overtopping of the levees and flooding of homes in the mandatory evacuation areas behind the levees. These levees were not part of the $14.5 billion levee upgrade New Orleans got after Hurricane Katrina, and were not rated to Category 3 hurricane strength, like the levees protecting New Orleans are. The surge continued upriver, elevating the water levels 10' in New Orleans (103 miles upstream from the mouth of the Mississippi), 8' in Baton Rouge (228 miles upstream), and 1.4' at Knox Landing, an amazing 314 miles upstream. The river was 7' low due to the great 2012 U.S. drought, and I suspect the near-record low flow rate of the river allowed the storm surge to propagate so far upstream. The salt water from the storm surge will be slow to leave the river, due to the continued winds of Isaac keeping the surge going, plus the very low flow rates of the river. One benefit of the heavy rains of 10 - 20 inches expected to fall over Louisiana over the next two days will be to increase the flow rate of the Mississippi River, helping flush the salt water out of the river. The low flow rates of the Mississippi had allowed salt water to move upriver to just south of New Orleans over the past few weeks, threatening the drinking water supply of Plaquemines Parish.


Figure 2. Tide gauge data from Waveland, Mississippi. The green line shows the storm surge. The red line is the storm tide, the height of the water above Mean Sea Level (MSL.) The storm tide at Waveland currently (9') is 2' higher than that of Category 2 Hurricane Gustav of 2008. Image credit: NOAA Tides and Currents.

Tropical Storm Kirk in the Central Atlantic
Tropical Storm Kirk formed Tuesday night in the Central Atlantic. Kirk's formation at 03 UTC on August 29 puts 2012 in 4th place for earliest formation date of the season's 11th storm. Only 2005, 1995, and 1933 had an earlier formation date of the season's 11th storm. Kirk should stay well out to sea and not trouble any land areas.


Figure 3. Morning satellite image of Tropical Storm Kirk.

Invest 98L in the Eastern Atlantic
A tropical wave (Invest 98L) is about 750 miles west-southwest of the Cape Verde Islands, and is moving west to west-northwest at about 15 mph. In their 8 am EDT Tropical Weather Outlook, NHC gave 98L a 50% chance of developing by Friday morning. Several of the models develop 98L into a tropical depression by this weekend, but none of the reliable models foresee that 98L will be a threat to the Lesser Antilles. The storm may be a threat to Bermuda next week, but it is too early to say if it may threaten the U.S.

Jeff Masters

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Quoting GTcooliebai:
This is so sad...Guys this is from a Cat. 1 Hurricane, please leave if you know your area is flood prone.

Plaquemines levee breached.Cant personally authenticate,but very possible (via Carl Parker)

MT @JMLeblanc23 from 3 story Braithewaite home

The photo you posted is a true picture from Braithwaite in Plaquemines if we are to believe the livestream from wwltv this morning. (And I do.) Complicated story in this case. The way I understand what I have heard today on wwl, has to do with new wall completed on the west bank, an ongoing levee improvement on the east bank, and the angle of the storm and its wind which drove gulf water straight upriver to meet water flowing downstream in the Mississippi. Lots of water with no place to go.
Member Since: October 9, 2005 Posts: 13 Comments: 499
Member Since: August 6, 2011 Posts: 4 Comments: 42277
Quoting RadarRich:
Hello Folks. Been watching StormJunkie and CycloneOz. Both chasing Hurricane Isaac in Miss. and La. Both are very interesting and, in Oz's case, entertaining, to say the least.
Personally, after following Isaac from his initial tropical wave days, I Still Am Amazed Currently. Since his eventual development, he has been an Indifferent Storm Against All Consensus. The models have been like windshield wipers throughout. The track has been tough. If Someone Actually Assumed Correctly, they would be considered a wizard. Ironically, Storms Are About Confusion, and not straight to the point entities. As we know about forecasting In Storms, Absolute Accuracy Counts, and is hoped for but, usually never happens. Ideologically, Storms Are Actually Confusing and do tend to make us all go nuts. This blog does occasionally go off the wall and thus Insane Stubborn Arguments Are Created. If Some Actually Agreed Coherently now and then, I believe we would take a pause and ask, is this the WU?? As we all do know, Ignorant Statements Are Always Condescending in one manner or another. However, in general, I think this blog is very interesting, entertaining, and knowledgeable. Thanks for keeping up the good work folks.
I Submit, Always Argue Civilized everyone. Isaac is one heck of a Cat 1, to say the least.

I sense an alarming Cerebellum.
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Quoting kwgirl:
Is everyone forgetting that it is also a Full moon or almost and that causes tides to be higher.
Good catch, forgot about that.
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Quoting RadarRich:
Hello Folks. Been watching StormJunkie and CycloneOz. Both chasing Hurricane Isaac in Miss. and La. Both are very interesting and, in Oz's case, entertaining, to say the least.
Personally, after following Isaac from his initial tropical wave days, I Still Am Amazed Currently. Since his eventual development, he has been an Indifferent Storm Against All Consensus. The models have been like windshield wipers throughout. The track has been tough. If Someone Actually Assumed Correctly, they would be considered a wizard. Ironically, Storms Are About Confusion, and not straight to the point entities. As we know about forecasting In Storms, Absolute Accuracy Counts, and is hoped for but, usually never happens. Ideologically, Storms Are Actually Confusing and do tend to make us all go nuts. This blog does occasionally go off the wall and thus Insane Stubborn Arguments Are Created. If Some Actually Agreed Coherently now and then, I believe we would take a pause and ask, is this the WU?? As we all do know, Ignorant Statements Are Always Condescending in one manner or another. However, in general, I think this blog is very interesting, entertaining, and knowledgeable. Thanks for keeping up the good work folks.
I Submit, Always Argue Civilized everyone. Isaac is one heck of a Cat 1, to say the least.


Nice!
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Quoting Bluestorm5:
Even though it's only a Category 1, this was a Category 3 surge IMO. Look at this video from Reed Timmer... hate him or not, he had captured the true force of what big Cat. 1 hurricanes could do with Category 3 surge.

Link
Is everyone forgetting that it is also a Full moon or almost and that causes tides to be higher.
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Member Since: August 6, 2011 Posts: 4 Comments: 42277
533. Your statements confound logic... a group is more at fault because they didn't repeal something, than the group that put the law into place? Um, ok.

Anyway... why the heck are we talking politics, when a tropical storm is trying to flood out a large city?
Member Since: August 3, 2008 Posts: 16 Comments: 5891
Can we leave the non-weather-related political discussions to a political blog?

There's two active storms and a soon-to-be TD12 in the Atlantic basin. Let's talk about that.
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Quoting icmoore:


I am just asking that we don't discuss personal irresponsibility at the very moment that people are suffering and possibly dying? Not everyone stayed so they could have a hurricane party...I am not trying to single you out but there have been so many insensitive and pompous comments by many so bloggers today...
Well said.
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Pretty strong trough that should pull 98L out to sea.

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Quoting Bluestorm5:
And proved that New Orleans area will need to work harder on their levees... this was too close for New Orleans area and new levees. Many levees failures in other area of Louisiana as well, even though there wasn't enough money/time since Katrina to prevent these failures from Isaac.


I wouldnt say that...water came from lake ponchartrain to the levees and never had a shot at getting over...
Worse thing that could have happened would have been the industrial canal overflowing for a few minutes, which wouldnt have done anything really.

Everything was under control
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Issac has often defied logic during his life span and it continues to this moment........He was weak at times when he was supposed to strengthen and has continued to remain strong when he was supposed to weaken.
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Very deadly storm affecting most of Louisiana, Mississippi, and Alabama.

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Real story from a father in LA -

Yesterday, I sent my family to AL to avoid Hurricane Isaac. After they left, I went to feed the family fish and I found the enclosed scene (See picture)--where my daughter , Ashley, had given good instruction on how her stuffed animal friends should behave during the Hurricane. ( A future leader in the making! ) - Greg Taylor - Mandeville LA

Ashley's Hurricane Isaac rules to stuffed animals:

1. Noises: scoot close to your buddy.
2. Bathroom: take a buddy.
3. Rules: follow these rules.
4. When I'm gone: stay calm. No parties.
5. Fun: have fun.
Member Since: August 16, 2007 Posts: 0 Comments: 614
Quoting JonClaw:


Hopefully she'll be pretty to watch leave, heh?


Precisely.

Usually, I expect at least one wet CV storm to make an NC landfall (it's usually what we need to break our seemingly-annual droughts), but this year has been so wet, that I fear even a low-Cat 1 could do as much damage as Fran or Floyd (in terms of downed trees and flooding).
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Wow! This is crazy!!! Posting from Uptown in NOLA. We are still experiencing very strong gusts. A handful of trees down in the neighborhood and I expect more to follow since many of them are old and won't be able to take much more. Still not experiencing very heavy rainfall, although it's pretty continuous. Haven't seen any flooding in my area at all, thank goodness. Be safe and well to everyone feeling Isaac's wrath
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Quoting jascott1967:


I'm just on the road on FM518. Been a super nice day here.


Feels good with the wind
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BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
353 PM EDT WED AUG 29 2012

THE NATIONAL WEATHER SERVICE IN GREENVILLE-SPARTANBURG HAS ISSUED A

* FLASH FLOOD WARNING FOR...
CENTRAL UNION COUNTY IN THE PIEDMONT OF NORTH CAROLINA...

* UNTIL 700 PM EDT

* AT 351 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
SLOW MOVING THUNDERSTORMS WITH VERY HEAVY RAINFALL ACROSS THE
WARNED AREA. RADAR ESTIMATES THAT 3 TO 4 INCHES OF RAIN HAS FALLEN
IN THIS AREA OVER THE PAST TWO HOURS IN THE VICINITY OF UNIONVILLE.

* RUNOFF FROM THIS EXCESSIVE RAINFALL WILL CAUSE FLASH FLOODING TO
OCCUR. SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...
MONROE...FAIRVIEW...MARSHVILLE...UNIONVILLE AND WINGATE. STREAMS
THAT WILL BE AFFECTED INCLUDE CROOKED CREEK...STEWARDS CREEK AND
RICHARDSON CREEK.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

EXCESSIVE RUNOFF FROM HEAVY RAINFALL WILL CAUSE FLOODING OF SMALL
CREEKS AND STREAMS...URBAN AREAS...HIGHWAYS...STREETS AND UNDERPASSES
AS WELL AS OTHER DRAINAGE AREAS AND LOW LYING SPOTS.
Member Since: August 6, 2011 Posts: 4 Comments: 42277
maybe this this track...recurving out to sea and not touching Canada though..
its too early to tell though...
Member Since: April 23, 2011 Posts: 104 Comments: 14873
523. Relix
Quoting tropicfreak:



But it has been trending further west. This isn't 2011 or 2010. The troughs are weaker, there is more ridging in place. Not saying it will be a US hit, so I could be wrong, but just saying that the factors are in place...


That's why I believe it will be closer than what the models suggest. Not too worried ATM since its gaining strength it seems, but I don't expect an Earl(2010) type of approach to us in the NE Islands.
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Quoting sunlinepr:


Not blaming any agency, neither government.... blaming personal decision, the ability to learn from the past....

Look in YTube for info, and you will see how many irresponsible videos of hurricane parties and nonsense.... while there is disaster around...


I am just asking that we don't discuss personal irresponsibility at the very moment that people are suffering and possibly dying? Not everyone stayed so they could have a hurricane party...I am not trying to single you out but there have been so many insensitive and pompous comments by many so bloggers today...
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Quoting RitaEvac:


200+ miles


Thanks, I looked it up, 248 miles from Houma-Galveston.

That's a big shield.
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Hello Folks. Been watching StormJunkie and CycloneOz. Both chasing Hurricane Isaac in Miss. and La. Both are very interesting and, in Oz's case, entertaining, to say the least.
Personally, after following Isaac from his initial tropical wave days, I Still Am Amazed Currently. Since his eventual development, he has been an Indifferent Storm Against All Consensus. The models have been like windshield wipers throughout. The track has been tough. If Someone Actually Assumed Correctly, they would be considered a wizard. Ironically, Storms Are About Confusion, and not straight to the point entities. As we know about forecasting In Storms, Absolute Accuracy Counts, and is hoped for but, usually never happens. Ideologically, Storms Are Actually Confusing and do tend to make us all go nuts. This blog does occasionally go off the wall and thus Insane Stubborn Arguments Are Created. If Some Actually Agreed Coherently now and then, I believe we would take a pause and ask, is this the WU?? As we all do know, Ignorant Statements Are Always Condescending in one manner or another. However, in general, I think this blog is very interesting, entertaining, and knowledgeable. Thanks for keeping up the good work folks.
I Submit, Always Argue Civilized everyone. Isaac is one heck of a Cat 1, to say the least.
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So why, if we're on the West side, are they still showing rainfall totals of 6-12" where we are? If it's sliding NW from it's current position, wouldn't it slide slightly East of us but we would still be in the brunt of the storm near the eye since it's moving at an angle and not straight up?
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Quoting midgulfmom:


Hi... Still no power and hot and humid...duh I know. Rain to come? Re: comment the water is coming from lakes and bayous round about the new great flood wall across the MRGO. All that water that has been stopped has to go somewhere and the new pressure now is to the lakes etc to the east. Areas that never flooded before got water and more water funneled now to lakes to the east. Yes technically...it's all from the gulf though.


Sigh........
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Quoting DVSmith:
Given the rapid development forecast in the intensity models, let's hope 98L recurves out to sea.


Hopefully she'll be pretty to watch leave, heh?
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Quoting trHUrrIXC5MMX:
Guys I have a question for you..

Did USA and the countries that can be affected by hurricanes like Mexico, Canada, Nicaragua, Costa Rica, Belize (UK), Azores etc. got into an agreement so that the NHC in Miami, FL USA is the sole authority to determine the status and tracking of any tropical cyclone in the Atlantic and Epac and no other country?

who can answer that?




http://en.wikipedia.org/wiki/Regional_Specialized _Meteorological_Center
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Quoting Relix:
98L should surely go NE of us. Definitely closer than what models are saying but at a nice distance.


But it has been trending further west. This isn't 2011 or 2010. The troughs are weaker, there is more ridging in place. Not saying it will be a US hit, so I could be wrong, but just saying that the factors are in place...
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Quoting NSB207:
As the hurricane moves northward, through LA, AK, and further north, is it possible its influence might break the dry high over the mid west and TX?

Seems there would be a disruption in the pattern...what is the history of weather changes in the past regarding this question.


It's going to Alaska? Levi might get some tropical action after all. :-)
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Quoting TropicalAnalystwx13:
As bad as this storm has been, imagine if it were a Category 3 or Category 4 like would have occurred if it built up a well-defined core several days before landfall. As it stands, the damage total will likely be over $2 billion.
And proved that New Orleans area will need to work harder on their levees... this was too close for New Orleans area and new levees. Many levees failures in other area of Louisiana as well, even though there wasn't enough money/time since Katrina to prevent these failures from Isaac.
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Quoting oracle28:


The cloud shield has reached Galveston Bay? How many miles is that from the center?


So...it did go west, along the coast. Looks to be more NW now, so maybe it won't decide to sneak back into the GOM. That would be a dangerous scenario for the Galveston area.
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Quoting RitaEvac:
Looking east towards Galveston Bay, Isaac cloud shield closing in







I'm just on the road on FM518. Been a super nice day here.
Member Since: August 16, 2007 Posts: 0 Comments: 614
Quoting CybrTeddy:


GFS said that about Isaac, then killed it off, then had it developing in the Caribbean and then all the drama we saw happened began. Euro doesn't even want to develop 98L. Euro seems to do the best with fully developed cyclones from what I've seen, as it has dropped a lot of storms this season.


ECMWF doesn't use bogusing, which could play a role in that. GFDL, GFDN, HWRF, NOGAPS, and UKMET do.
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Given the rapid development forecast in the intensity models, let's hope 98L recurves out to sea.
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BREAKING: 5.2 VIRGIN ISLANDS QUAKE
Member Since: April 23, 2011 Posts: 104 Comments: 14873
From New Orleans, LA:

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Quoting LAlurker:

Downstream? The water came from the Gulf.


Hi... Still no power and hot and humid...duh I know. Rain to come? Re: comment the water is coming from lakes and bayous round about the new great flood wall across the MRGO. All that water that has been stopped has to go somewhere and the new pressure now is to the lakes etc to the east. Areas that never flooded before got water and more water funneled now to lakes to the east. Yes technically...it's all from the gulf though.
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Even though it's only a Category 1, this was a Category 3 surge IMO. Look at this video from Reed Timmer... hate him or not, he had captured the true force of what big Cat. 1 hurricanes could do with Category 3 surge.

Link
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Quoting vince1:
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502. Relix
98L should surely go NE of us. Definitely closer than what models are saying but at a nice distance.
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Quoting VirginIslandsVisitor:


Thanks for the info, Taz!



welcome



keep a eye on the mode runs even no they show out too sea now they could all change and hit land
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Quoting pottery:

Thanks, Taz!
I've been watching that today.

Hoping it goes out to sea, but too early to know.....



welcome
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Quoting Tazmanian:
if you live in PR or the Lesser Antilles i would keep a vary close eye on 98L has some of the mode runs are start too point tours you




Thanks for the info, Taz!
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As the hurricane moves northward, through LA, AK, and further north, is it possible its influence might break the dry high over the mid west and TX?

Seems there would be a disruption in the pattern...what is the history of weather changes in the past regarding this question.
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I was bored and decided to compare Aug 2004 with Aug 2012 (permitting formation of 98L!);

2012 has had all but one day where a functioning cyclone (or its remnants) existed, where 2004 had roughly five days. The way 2004 wins out though is through the power of the individual systems (3 majors, while we nearly made it with one [Gordon]).

Pretty rapid start to August!

P.S. Hurricane Alex (2004) also formed into a named system on 1st August. See any similarities in our current season, with exception of power of the systems as mentioned above.

Found it quite interesting is all.
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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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