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 groundedpilot:
Just got power back in New Iberia ! Anybody hear about a levee break around Madisonville ?

Haven't heard anything about Madisonville, there was a significant breach in Braithwaite.
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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...


I was the one who made the statement about the hurricane party and I only posted on what I saw on Good Morning America this morning which is national news..I never said everyone chose to party..I specifically said in New Orleans that they were having hurricane parties..if anyone want to gripe about that, then take it up with ABC news as its online on their website by reporter Bill Weir..I also posted in defense of those who didnt evacuate and even stated that the economy is bad and people are living from pay check to pay check and not everyone can up and leave to ride out a storm in a hotel/shelter due to financial and health reasons..as much as people here want to defend some, Im sure there were some who just thought it was a Cat 1 storm and refused to leave even with the means to do so..did they deserve to lose their homes..heck no! Also to state people are possibly dying is premature as I havent read or seen anything like that and I pray it dosent happen..we need to be more optomistic and stop making things appear worse than they really are..yes property has been lost but there is always living another day and able to hug your love ones..I will take that any day over materalistic possessions..Im sure Haiti islanders will disagree about people staying in mandatory evacuations when they had a choice to leave..remember, there is always someone who has it harder than all of us..blessings to all in the path of Isaac
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Quoting LargoFl:
amazing, still has an eye...................


Pretty amazing huh?
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Quoting LargoFl:
amazing, still has an eye...................


yeah, been over me in assumption parish for a while now...in the early morning hours the feeder bands were being weakened by the dry air...however, when the stronger bands in the eye wall got here at 5 am this morning, all hell broke loose. I was able to get power back at noon today and internet just came up....one of the luck ones for now.
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Quoting alaina1085:

Ascension Parish... 60 miles north east of NOLA and 20 miles south east of Baton Rouge.


Gonzales?
Member Since: July 14, 2008 Posts: 2 Comments: 9680
Quoting groundedpilot:
Just got power back in New Iberia ! Anybody hear about a levee break around Madisonville ?


NOLA.com ‏@NOLAnews

Hurricane #Isaac causes levee break at Guste Island near Madisonville; search and rescue under way - http://ow.ly/dkgRE
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Quoting MrMixon:


I thought radar tended to underestimate precipitation... and isn't it still raining?


Getting some of the heaviest rains right no win Baton Rouge..
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We will tie with 2011 and 2005 for a second time if Leslie is designated tomorrow.

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Quoting alaina1085:

Ascension Parish... 60 miles north east of NOLA and 20 miles south east of Baton Rouge.
that is where all my husbands family is - I have a niece lives on Cypress Bend Ave on a pond that looks just like that in Gonzales.
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Thanks to Largo and all others providing updates and photos. Watching and hoping for the worst of the damage to be to stuff instead of people and their pets.
Member Since: August 26, 2012 Posts: 0 Comments: 368
Quoting gbreezegirl:
This looks familiar. I think I have relatives live there. Where was this taken?

I live in Galvez/Gonzales of hwy 933
Member Since: August 2, 2006 Posts: 0 Comments: 1240
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...
I think is a matter of timing, between the trough and the forward movement of 98L. We are also getting closer to the first half of September, climatologically speaking most of the strongest band more damaging hurricanes have affected the North eastern Caribbean an Puerto Rico during this time.Let's see what happens...not to sure it will curb before reaching 60W...
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582. FOREX
Quoting GTcooliebai:
That is true, sometimes if a trough is too weak and the storm is too far south it won't be able to feel the influence from the trough and continue on a westward track, as the high builds in over head after the trough lifts up or passes.


Right. I learn a lot from your posts. Where do you live?
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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 Taz...will be watching it
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Just got power back in New Iberia ! Anybody hear about a levee break around Madisonville ?
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Quoting gbreezegirl:
Love it. Anyone know anything about Ascension parish in LA? I haven't heard from the relatives in a while and I am starting to get a little worried.

Give Bill Gates a few trillion dollars, what does he do, start messin with the weather on psilocybins. /sarc

Missing quite a few of our peeps reporting tonight, power outs maybe more widespread. Do your relatives know to text, not call in these scenarious?
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Quoting gbreezegirl:
Where are you at??

Ascension Parish... 60 miles north east of NOLA and 20 miles south east of Baton Rouge.
Member Since: August 2, 2006 Posts: 0 Comments: 1240
Quoting alaina1085:

Our pond never gets this high.... Im afraid we will be getting sand bags if this keeps up. We have hours of rain and wind left.
This looks familiar. I think I have relatives live there. Where was this taken?
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Quoting FOREX:


I'm still learning about troughs and such from this blog. I know I've read that sometimes storms are too low a latitude to be picked up.
That is true, sometimes if a trough is too weak and the storm is too far south it won't be able to feel the influence from the trough and continue on a westward track, as the high builds in over head after the trough lifts up or passes.
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Quoting RitaEvac:
Nowhere near 15-20 inches of rain that was thought to play out


West Palm Beach got over 20" after the storm was gone. They were still getting rain yesterday. My brother just called from Central Fl, saying they were getting another feeder band. It's far from over.
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Quoting LargoFl:
amazing, still has an eye...................
Not really...plenty of fuel.
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Quoting alaina1085:

Our pond never gets this high.... Im afraid we will be getting sand bags if this keeps up. We have hours of rain and wind left.
Where are you at??
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...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 445 PM CDT FOR
SOUTHERN TANGIPAHOA...LIVINGSTON...EAST BATON ROUGE AND ASCENSION
PARISHES...

AT 317 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED VERY
HEAVY RAIN CONTINUING ACROSS THE WARNED AREA ASSOCIATED WITH BANDS
FROM TROPICAL STORM ISAAC. THE MODERATE TO HEAVY RAINFALL WILL
CONTINUE INTO THE EVENING HOURS. ADDITIONAL RAINFALL AMOUNTS OF 2
TO 4 INCHES WITH LOCALLY HEAVIER AMOUNTS WILL BE POSSIBLE THROUGH
EVENING.
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Quoting RitaEvac:
Nowhere near 15-20 inches of rain that was thought to play out



I thought radar tended to underestimate precipitation... and isn't it still raining?
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568. FOREX
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.


I'm still learning about troughs and such from this blog. I know I've read that sometimes storms are too low a latitude to be picked up.
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Quoting tjboudreaux:


We've been getting a good bit of rain and wind in Henderson.
I think part of the rain is still stuck in Mobile - looks like we might get a little more in my area (pensacola) soon.
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Our pond never gets this high.... Im afraid we will be getting sand bags if this keeps up. We have hours of rain and wind left.
Member Since: August 2, 2006 Posts: 0 Comments: 1240
12z UKMET 120 hrs.

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amazing, still has an eye...................
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Can 542 be nominated for the WU hall of fame?
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Quoting VirginIslandsVisitor:
Just watched StormJunkie run for cover when a very violent storm came through. Gotta admire his driving ability. Those were big winds and rain. Someone just told him that CNN is going to be streaming him. Very interesting.

Link


I will be on St John over the Labor Day weekend for my daughters wedding. Saw a post about a 5.4 earthquake and 98 is off the coast of Afreca. Any comments about my coming week that you could give.
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Quoting redwagon:

I sense an alarming Cerebellum.
Love it. Anyone know anything about Ascension parish in LA? I haven't heard from the relatives in a while and I am starting to get a little worried.
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Quoting CybrTeddy:


The first few are from Waveland MS, which if anyone follows Reed Timmer on facebook would already know where he is, the rest are in Braithwaite, LA I believe.


I don't know who Reed Timmer is and I don't do FB. As I said, caption your photos if you know where they are. You might be amazed at the number of people who don't know a guy named Reed Timmer or who are on FB.
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Quoting RitaEvac:
Nowhere near 15-20 inches of rain that was thought to play out


Halfway to 20" in some spots, and it's not over yet. Could reach 15" yet.
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rom NWS Jackson, MS: Sounds like conditions are deteriorating in the Highway 98 coridor. Getting reports of frequent 40 mph gusts in Columbia with increasing trees down and power outages. Also some flooding.
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Quoting CaicosRetiredSailor:




http://en.wikipedia.org/wiki/Regional_Specialized _Meteorological_Center


Talking for Honduras we like to make things Big time. Hurricanes 12,000+ deaths , violence 3000 dead a month. Hunger 5000 a year deaths. SO why we would worry to finance something so simple as 12 ,48.5 million us$ planes for the only reason ,that somebody can argue this is not a cat 1 its a cat3 , forget about it.

Do things big or just don't do it.JAJAJAJAJA

Ohh wait scientific data who cares. Our political system is already to busy to worry about science.

So thxs usa citizens for using your money so we can be safe.Because our own goverment doesn't care.
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556. rco3
Vince, Nea, CJ5: No, how about we DON'T start. There is a landfalling hurricane RIGHT NOW, and you people are again dragging your stinky politics into the blog. Ignore the bait. Take it elsewhere. Just quit bringing it here. It may have started as a discussion of FEMA and its role in emergencies like this (on-topic), but discussion of educational budgets and which administrations are more responsible spenders is off-topic.

"When using Dr. Masters' blog, please refrain from posting material not relevant to the discussion of tropical weather, or the topic of the blog entry itself." I know this is hard to believe, but that means you too.
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Quoting GTcooliebai:
Pretty strong trough that should pull 98L out to sea.





98L is too far S and its still ways a way from that trough
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BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE JACKSONVILLE FL
402 PM EDT WED AUG 29 2012

THE NATIONAL WEATHER SERVICE IN JACKSONVILLE HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
NORTHWESTERN ATKINSON COUNTY IN SOUTHEAST GEORGIA
COFFEE COUNTY IN SOUTHEAST GEORGIA

* UNTIL 430 PM EDT

* AT 402 PM EDT...NATIONAL WEATHER SERVICE METEOROLOGISTS WERE
TRACKING A SEVERE THUNDERSTORM CAPABLE OF PRODUCING DAMAGING WINDS
IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED NEAR WILLACOOCHEE...
AND MOVING NORTHEAST AT 20 MPH.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO WEST
GREEN...PRIDGEN...DOUGLAS...BROXTON AND AMBROSE.
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Quoting RussianWinter:
BTW is 98L pretty much guaranteed to be a fish storm?


I have 98L coming into Corpus Christi Sometime mid September as a Cat-3 storm...If you just shook your head then I bet you had Isaac riding up the East coast didn't you. FUN SEASON!!
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Quoting JasonRE:
Lafayette still not seeing rain. Wow......where is it?


We've been getting a good bit of rain and wind in Henderson.
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Nowhere near 15-20 inches of rain that was thought to play out

Member Since: July 14, 2008 Posts: 2 Comments: 9680
549. yoboi
Quoting JasonRE:
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?



counter clockwise......
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folks if you have phone contact with anyone cut off and no power in the danger zones, an official said crews would get to work on repairing the lines etc..when the winds get 30 mph or lower..there are alot..of crews standing by, just hold on and stay safe..
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Quoting CJ5:


Please don't start, but since you did. Lets talk real numbers; Head Start a program that every single study proves provides no benefit costs us 8 billion a year and 81 billion since the 70's. Cut it. Student grades have remained level since the 70's despite a 300% increase in funding. The Federal Education department has served no function that relates to improved learning for children, none. There may be some need in federal involvement but it should all go back to the local level. The Teachers Union is the 6th largest contributor to politicians, well ahead of Big Oil. Tax cuts didn't cause the problem, if they did this Administration is even more to blame because they didn't repeal them. So lets talk about how to cut spending and quit blaming straw men.


Stop having Natural Disasters, would be a good start. Simple.

Now, please, for the sake of us out here who don't give a dam about the state of US Domestic Administration, stop the talk.
Member Since: October 24, 2005 Posts: 0 Comments: 24799
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.
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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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