Isaac slamming Gulf Coast with damaging floods, tornadoes

By: Dr. Jeff Masters , 4:44 PM GMT on August 30, 2012

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Slow-moving Tropical Storm Isaac continues to hammer coastal Louisiana, Mississippi, Alabama, and Florida's Panhandle with tornadoes, torrential rains, high winds, and a damaging storm surge. Over the past 24 hours, destructive tornadoes have touched down in Biloxi and Pascagoula, Mississippi, and one person was killed by a tree falling on a car in Pearl River County, Mississippi. A major flood event is occurring in Slidell, Louisiana, where Isaac's storm surge filled Bayou Bonfouca and the W-14 Canal, inundating portions of the city with 1 - 5 feet of water. While Isaac is now a weakening minimal-strength tropical storm, it is still a potent rainmaker, and will cause damaging floods all along its path for the next three days. Major river flooding is occurring or is about to occur on a number of rivers in the landfall area. In north central Tangipahoa Parish in southeast Louisiana and southwestern Pike County in southern Mississippi, a mandatory evacuation has been ordered for all low-lying areas and along the Tangipahoa River, due to the potential failure of the Lake Tangipahoa dam. Audubon Park in New Orleans, recorded 11.19" of rain as of 7 pm Wednesday night. An earlier amount of 19" was found to be erroneous, and this is not a 24-hour precipitation record for the city. According to wunderground's weather historian, Christopher C. Burt, New Orleans' greatest 24-hour rainfall on record is 14.01" on July 24 - 25, 1933. The Louisiana official state 24-hour record is 22.00" on Aug. 29, 1962 at Hakberry, although U.S. Army Corps of Engineers `Storm Studies' mentions a 23.80" falling in a 24-hour period at Millers Island during a TS on Aug 7-8, 1940. Storm total was 37.50" over a 60-hour period there during that event.

A few other rainfall totals from Isaac, through 11 am EDT on Thursday:

15.02" Marion, MS
10.09" Hattiesburg, MS
10.15" Gulfport, MS
9.80" Slidell, LA
9.74" Biloxi, MS
8.52" Mobile, AL
5.57" Baton Rouge, LA


Figure 1. Isaac's winds and storm surge overcomes the seawall and floods South Beach Boulevard in Waveland, Miss., Wednesday, Aug. 29, 2012, the seventh anniversary of Hurricane Katrina hitting the Gulf Coast. (AP Photo/Rogelio V. Solis). Waveland experienced a storm surge in excess of 5' for 36 hours.

Isaac's storm surge winds down
Storm surge levels along the coast of Mississippi and surrounding areas are gradually receding, and the surge has finally fallen below 5' at Waveland, which experienced a storm surge in excess of 5' for 36 hours. Isaac's storm surge levels were characteristic of a Category 2 hurricane, and lasted for an exceptionally long period of time. Waveland, Mississippi experienced a peak surge of 8' and peak storm tide of 9' (surge plus the natural high tide), which beat the levels that occurred during Category 2 Hurricane Gustav of 2008 (7' of storm tide.) The peak 11.06' storm surge at Shell Beach, which is in Lake Borgne, 30 miles southeast of New Orleans, exceeded the 9.5' surge recorded there during Gustav. According to an article in nola.com, Isaac pushed a storm surge of 13.6' into Lake Borgne, on the east side of New Orleans. This is not far from the 15.5' storm surge Hurricane Katrina brought to the location. It is quite possible that Isaac's storm surge might have breached levees of the east side of New Orleans, flooding areas inhabited by tens of thousands of people, had the Army Corps of Engineers not completed their $14.5 billion upgrade to the New Orleans flood defenses this year. I estimate that storm surge damage from Isaac will exceed $2 billion. Isaac has likely caused $2.5 billion in insured damage not related to flooding, insurance firm Eqecat estimated yesterday. Here were some of the peak storm surge values that were recorded at NOAA tide gauges during Isaac:

11.1' Shell Beach, LA
8.0' Waveland, MS
3.5' Pensacola, FL
4.6' Pascagoula, MS
3.8' Mobile, AL


Figure 2. A TRMM satellite 3-D view of rainfall on Aug. 28 showed a few very powerful thunderstorms near Isaac's eye were reaching heights of almost 17 km (10.6 miles.) Intense bands of rain around Isaac were occasionally dropping rain at a rate of over 2.75 inches per hour. Image credit: SSAI/NASA, Hal Pierce.

Isaac's storm surge on the Mississippi River
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. Since salt water is more dense than fresh water, the surge travelled along the bottom of the river, with the fresh water flow of the river lying on top. The surge continued upriver, and before reaching New Orleans, encountered an underwater barrier in Plaquemines Parish. This barrier was constructed by the Army Corps of Engineers beginning on August 15, in order to keep salt water from moving upstream and contaminating drinking water for Plaquemines Parish and New Orleans. Salt water had made it 90 miles upriver to the outskirts of New Orleans, due to the low flow rate of the river (which had dropped 7' below average in height due to the drought of 2012.) According to a spokesperson for the National Weather Service River Forecast Office, this barrier was probably able to completely block the flow of salt water upriver due to Isaac's storm surge, and no salt water made it as far as New Orleans. However, the massive intrusion of ocean water into the river channel caused the mighty Mississippi's fresh water flow to back up for hundreds of miles. Water levels were elevated by 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.

Hurricane Kirk in the Central Atlantic
Hurricane Kirk intensified into a 75 mph Category 1 hurricane this morning, becoming the busy 2012 Atlantic hurricane season's fifth hurricane. With the season's mid-point of September 10 still almost 2 weeks away, we've already had 12 named storms and 5 hurricanes, which is close to what an entire season experiences in an average year (11 named storms and 6 hurricanes.) Kirk should stay well out to sea and not trouble any land areas.


Figure 3. Morning satellite image of Hurricane Kirk.

Tropical Storm Leslie forms in the Central Atlantic
Tropical Storm Leslie has formed in the Central Atlantic. Leslie's formation on August 30 puts 2012 in 2nd place for earliest formation date of the season's 12th storm. Only 1995 had an earlier formation date of the season's 12th storm. With records dating back to 1851, this year is only the second time 8 total storms have formed in August. The other year was 2004, when the first storm of the season formed on August 1 (Alex), and the 8th storm (Hermine)
formed on August 29th. Leslie is organizing quickly, and appears destined to become a hurricane before the week is out. Fortunately, Hurricane Kirk is weakening the ridge of high pressure to the north of Leslie, and Leslie is expected to turn to the northwest and miss the Lesser Antilles Islands. In the long term, it remains unclear if Leslie will follow Kirk and fully recurve out to sea. The latest 2 runs of the GFS model have predicted that Leslie will recurve out to sea and not threaten any land areas, but the latest 2 runs of the ECMWF model have predicted that the trough of low pressure pulling Kirk to the northeast will not be strong enough to recurve Leslie out to sea. Instead, the ECMWF predicts that a ridge of high pressure will build in early next week, forcing Leslie more to the northwest, making the storm a potential threat to Bermuda, then to the Northeast U.S. and Canada in 8 - 11 days.

Jeff Masters

Hurricane Isaac Louisiana (apphotos)
Two men walk in the storm surge from Isaac, on Lakeshore Drive along Lake Pontchartrain, as the storm approaches landfall, in New Orleans, Tuesday, Aug. 28, 2012. (AP Photo/Gerald Herbert)
Hurricane Isaac Louisiana
west palm beach flood isaac (alishu)
West Palm Beach flood from Isaac
west palm beach flood isaac
Hurricane Isaac Impacts Navarre Beach & Pier10 (jennjeff1)
Hurricane Isaac versus Navarre Beach Pier, the longest concrete pier on the Gulf of Mexico
Hurricane Isaac Impacts Navarre Beach & Pier10

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788. JLPR2
Quoting PRweathercenter:
Lcould you send me the link for the bouy?


Sure.

Here is the buoy.

Here is the link to the buoy page.
Member Since: September 4, 2007 Posts: 7 Comments: 8748
Quoting Hurricanes305:


Have the same thin! Its a good Laptop in terms of speed however it the battery life can be deplorable at times!

Ok, I'll look for that.
Member Since: May 12, 2012 Posts: 15 Comments: 3093
786. JLPR2


Hmm... Suspicious looking arc in the deep convection, eye wall trying to form?
Member Since: September 4, 2007 Posts: 7 Comments: 8748
Quoting opal92nwf:
I am not an Accuweather person. So for all you people who know about him, how would you describe Joe Bastardi in a nutshell?

Squashed up real small.
Member Since: October 24, 2005 Posts: 0 Comments: 25383
Quoting AussieStorm:

Joe B is having a rant about the NHC. classic.

He talks too much.
Member Since: July 6, 2010 Posts: 113 Comments: 33567
Quoting KEEPEROFTHEGATE:
T.C.F.W.
12L/TC/L/CX
MARK
14.55N/46.76W


hey keep,

you see 'er making that WNW turn?
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Quoting opal92nwf:
I am not an Accuweather person. So for all you people who know about him, how would you describe Joe Bastardi in a nutshell?


Unprofessional shrill with meterological training.
Member Since: Posts: Comments:
Quoting Grothar:


in or as?

sorry for the colloquialism. I meant to say how would you briefly describe him?
Member Since: May 12, 2012 Posts: 15 Comments: 3093
Quoting TropicalAnalystwx13:
Kirk is likely going to hold at 90 mph for the 11pm EDT advisory, but Leslie should be up to 50 mph.

30/2345 UTC 28.5N 50.3W T4.5/4.5 KIRK -- Atlantic

30/2345 UTC 14.5N 45.7W T3.0/3.0 LESLIE -- Atlantic


I think Kirk will be a major hurricane and leslie also
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Quoting JLPR2:


Yeah, 1005mb, though 27mph winds aren't impressive.
Lcould you send me the link for the bouy?
Member Since: Posts: Comments:
T.C.F.W.
12L/TC/L/CX
MARK
14.55N/46.76W
Member Since: July 15, 2006 Posts: 186 Comments: 57610
Quoting beell:



Stormdrain,
This may have already been mentioned elsewhere.

If you wanted to pick a place on the River where a prolonged period of strong SE winds/surge in conjunction with a hurricane landfall could combine with a particular orientation of a protection levee (backlevee-not a mainline river levee) you might not find a much better set-up. A funnel.

SIL and family live on the West Bank across from Braithwaite. There here with us now. No power at the house. Semi-familiar with the area and similar issues in the past.

Thank you, beell, for your answer and for taking time to make the graphic. Makes sense.
:)

Guess the biggest ? I been trying to understand is whether the surge came upriver (as Plaquemines Parish President Billy Nungesser seemed to suggest in a news conference on wwltv Wednesday morning... perhaps I misheard him), over land/swamp, or both.

Best wishes to your family and to all who've been affected by Isaac.
Member Since: October 9, 2005 Posts: 13 Comments: 499
Quoting opal92nwf:

Dell Inspiron


Have the same thin! Its a good Laptop in terms of speed however it the battery life can be deplorable at times!
Member Since: May 25, 2012 Posts: 0 Comments: 2043
Hopefully they'll bring you some cheese to go with that whine. Clearly you don't have enough self awareness to know when you're embarrassing yourself. I feel sorry for the EOC staff having to deal with self centered whiners like you when there are actual serious things to be dealt with.

Quoting padirescu:


You should read and understand the context of the post before responding. The EOC took 8 hours to arrive with the water after they initially called 2 DAYS AFTER IT STOPPED RAINING.

Granted it wasn't 3 days later and I'm not here to discuss their lack of planning. What I am here to discuss is the county's lack of following through with what they communicate to the public.

"We'll get you what you need quickly." - 8 hours later
"We're going door to door to make sure everyone is ok" - Haven't seen anyone for the past 3 days since it stopped raining.
Member Since: Posts: Comments:
774. beell
Quoting opal92nwf:
I am not an Accuweather person. So for all you people who know about him, how would you describe Joe Bastardi in a nutshell?


In a nutshell..
Member Since: Posts: Comments:
Quoting opal92nwf:
I am not an Accuweather person. So for all you people who know about him, how would you describe Joe Bastardi in a nutshell?


Considering that he is a Penn State man this past year must have been very hard on him with the sex scandal/cover-up involving the heads of PS
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Quoting opal92nwf:

Dell Inspiron



cool
Member Since: May 21, 2006 Posts: 5092 Comments: 115682
Quoting PalmBeachWeather:
I have all kind of problems with that type of English..But I do have Dyslexia.... 5 out of 4 people have it

But remember, dyslexics are teople poo
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Quoting galvestonhurricane:
Good to see Isaac finally pulling away from Louisiana. Anyway, I need help with one of my AP Chemistry problems. Here it is: How would you synthesize chromyl chloride (CrO2Cl2)? What precautions might you take? Is it likely to be a liquid or a solid at ordinary temperatures, and what is its likely color?
Google has your answer!!hahaha
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Quoting Grothar:
Joe Bastardi's 2009 forecast and below are the actual tracks.
Well, he wasn't too far off; he said 12-8 or 13-8, and the actual was 9-3. And he called for 1 or 2 focused on the East coast, while none actually hit. But he was correct in calling for hurricane season to run from June through November, so I'll give him that. Of such things are greatness made...
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Quoting opal92nwf:
I am not an Accuweather person. So for all you people who know about him, how would you describe Joe Bastardi in a nutshell?


in or as?
Member Since: July 17, 2009 Posts: 71 Comments: 27511
Quoting serialteg:


greetings,

if i ever move from PR, im going to miss the excitement of hurricane season + the surfing...

unless i move to a surfing place :) with warm water?!?.



i've been caught 'layercasting' before and it hurt... :/


Not layer casting it just a generalization of the steering layers based on the current setup and trends.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
Quoting AussieStorm:


Joe Bastardi is on the show very soon

Joe B is having a rant about the NHC. classic.
Member Since: Posts: Comments:
What is everyone's feelings on the dam breaking and the manual breaching of it...........I'm afraid they will end up making it break and flood d/t pressure from water built up against it............plus aren't they still getting rain?
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Quoting Tazmanian:



give it too me give it too me i want it




what kind of laptop is it

Dell Inspiron
Member Since: May 12, 2012 Posts: 15 Comments: 3093
Quoting islandgirls:


.......Antigua and Barbuda......ok you've got my full attention.School officially starts on Monday. Luis came the Sunday (school was to officially start the Monday). Should we be impacted by Leslie on Sunday then I guess Luis left a message for Leslie.
Lol, will have a better idea tommorrow
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762. JLPR2
Quoting serialteg:


wow look at that DROP!!!!


Yeah, 1005mb, though 27mph winds aren't impressive.
Member Since: September 4, 2007 Posts: 7 Comments: 8748
Quoting galvestonhurricane:
Good to see Isaac finally pulling away from Louisiana. Anyway, I need help with one of my AP Chemistry problems. Here it is: How would you synthesize chromyl chloride (CrO2Cl2)? What precautions might you take? Is it likely to be a liquid or a solid at ordinary temperatures, and what is its likely color?


Try this Synthesis of Chromyl Chloride from the addition
of 98% H2SO4 to a mixture of KCl/K2Cr2O7
here is a video link to the this Synthesis of Chromyl Chloride or just google it!
Member Since: May 25, 2012 Posts: 0 Comments: 2043
Member Since: July 15, 2006 Posts: 186 Comments: 57610
Quoting mks:
Grothar, do you think that Leslie will get picked up by the through or might she miss the weakness and continue heading west?
If doesnt start turning west =northwest soon.looks that way.
Member Since: Posts: Comments:
I am not an Accuweather person. So for all you people who know about him, how would you describe Joe Bastardi in a nutshell?
Member Since: May 12, 2012 Posts: 15 Comments: 3093
Quoting JLPR2:


Leslie is closing in on this Buoy.


wow look at that DROP!!!!
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Quoting galvestonhurricane:
Good to see Isaac finally pulling away from Louisiana. Anyway, I need help with one of my AP Chemistry problems. Here it is: How would you synthesize chromyl chloride (CrO2Cl2)? What precautions might you take? Is it likely to be a liquid or a solid at ordinary temperatures, and what is its likely color?


Sorry, that's in my daughters' realm...and being I'm supposed to be in bed, she might get mad if she knew I was still up reading blog comments and asking her about a chemistry prob and thus...she knows I'm not 'really' in bed yet! LOL
Member Since: October 12, 2011 Posts: 0 Comments: 873
Quoting opal92nwf:
Commenting from my new laptop! (:



give it too me give it too me i want it




what kind of laptop is it
Member Since: May 21, 2006 Posts: 5092 Comments: 115682
Kirk is extremely beautiful. I think he may end up being like Gordon, only I think that Kirk will actually "officially" become a major hurricane. I think Gordon will be upgraded post season.

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Quoting Hurricanes305:
Slow blog tonight considering we have 2 strengthening tropical systems right now.


i think it's the lack of florida talk + hah...
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Near peak, obvs...

Atl
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Commenting from my new laptop! (:
Member Since: May 12, 2012 Posts: 15 Comments: 3093
Quoting JLPR2:


Traumatized by Isaac? :P

As far as I know that is the norm for a strengthening system.


greetings,

if i ever move from PR, im going to miss the excitement of hurricane season + the surfing...

unless i move to a surfing place :) with warm water?!?.

Quoting Hurricanes305:


The new 18z models pick up on the weakness that Kirk is creating north of Leslie thus having to storm follow the weakness. I must add the weakness has shrunk as the subtropical ridge have strengthen some in the latest steering layers. Because it shrunk leaves a tighter window of recurvature so in order to have a complete recurve out to sea like the early 18z model suggest a sharper turn must occur. However the storm is racing west at 20mph (which seems to be the norm since Ernesto) which mean if it miss a tightening window of recurvature it might get trap under the strengthen ridge before a second trough tries to pick it up but we shall see how strong the second one will be.


i've been caught 'layercasting' before and it hurt... :/
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Quoting washingtonian115:
I wonder if Joe Bastardi will be dooming and glooming the east coast about Leslie.Irene wasn't enough...


He apparently wants a repeat of either the 1635 Great Colonial Hurricane (Strongest Hurricane to ever hit New England) or the 1821 Norfolk and Long Island hurricane, one of the worst, if not the worst storm for the Eastern Seaboard.

Damage from a repeat of either would probably dwarf Katrina in cost and casualties. Considering who he donates to, I can hazard a guess why he fantasizes about it.

How is Kirk doing? Last I saw, the T-Numbers were at 5.0.
Member Since: October 4, 2007 Posts: 0 Comments: 451
Joe Bastardi's 2009 forecast and below are the actual tracks.








Member Since: July 17, 2009 Posts: 71 Comments: 27511
Quoting JLPR2:


Traumatized by Isaac? :P

As far as I know that is the norm for a strengthening system.

No, not traumatized by Isaac. CV storms moving W have had at least 4 centers each by the end of their run. Isaac was actually the least-multiple center.. until he split this morning, sending his MLC SE while his LLC became the tracked center.

And you're right, multiple centers are a norm now for strengthening storms. A few years ago, that wasn't the case. Nobody started arguing about a storm's path until the end, i.e. nearing landfall we convulsed about Wward jogs and stair-stepping. But now we have to speculate as CV storms aren't doing what they're supposed to at an earlier date than usual.
Member Since: August 4, 2007 Posts: 0 Comments: 3282
Slow blog tonight considering we have 2 strengthening tropical systems right now.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
18z GFS spread..look for the next set of ensembles to not be so clustered on leslie..




Member Since: Posts: Comments:
Good to see Isaac finally pulling away from Louisiana. Anyway, I need help with one of my AP Chemistry problems. Here it is: How would you synthesize chromyl chloride (CrO2Cl2)? What precautions might you take? Is it likely to be a liquid or a solid at ordinary temperatures, and what is its likely color?
Member Since: Posts: Comments:
Quoting PRweathercenter:

It seems possible, keep in mind the models and the nhc are going to need time to get a good handle on leslies track, this morning it was just a tropical wave, and tonight a tropical storm thats getting stronger, if it doesnt slow down, i think Antigua and Barbuda could have some tropical storm force winds!! Will see what happens with the ridge


.......Antigua and Barbuda......ok you've got my full attention.School officially starts on Monday. Luis came the Sunday (school was to officially start the Monday). Should we be impacted by Leslie on Sunday then I guess Luis left a message for Leslie.
Member Since: Posts: Comments:
.
Member Since: May 21, 2006 Posts: 5092 Comments: 115682
Quoting PalmBeachWeather:
If I can ever figure how to get out of the store with all of the long ramps leading nowhere
you can't park in the middle of those, have to pick an end, just remember calories burned getting out of there :)
Member Since: June 6, 2010 Posts: 0 Comments: 4467
Quoting WeatherNerdPR:

Nope. I don't think I'll be able to see frost in Puerto Rico. XD


remember the hail we had like two years ago? at least in san juan it was heavy... also in moca
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Kirk is likely going to hold at 90 mph for the 11pm EDT advisory, but Leslie should be up to 50 mph.

30/2345 UTC 28.5N 50.3W T4.5/4.5 KIRK -- Atlantic

30/2345 UTC 14.5N 45.7W T3.0/3.0 LESLIE -- Atlantic
Member Since: July 6, 2010 Posts: 113 Comments: 33567
Quoting PRweathercenter:
You know whats interesting, earl was actually a lot further north than leslie


Did you do a video update on Leslie and Kirk
Member Since: May 25, 2012 Posts: 0 Comments: 2043

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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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