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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Well here in Mobile, Al we finally started getting some heavy squalls last night and most of today. Have not lost power through the whole thing in my area although I have heard reports of spotty power outages in the Mobile area. We got lucky it didn't start that strengthening it went through yesterday the day before that or this would have made what is already a terrible situation considerably worse. Hopefully things will turn out good for most that took a much harder hit than myself did. Got to save my storm supplies yet again which is never a bad thing in my book, still a long ways to go this year and hoping the gulf and east coast avoid any storms that may form later. Thoughts and prayers are with everyone involved with this storm and for the ones that in for the flooding rains in the north when it finally decides to leave
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Quoting SubtropicalHi:
106 for a high in Corpus Christi today.
Unreal for a coastal city, even by Texas standards.

Wow, that's obscene that close to the Gulf!
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Quoting KRL:


Actually POLITICS directly impacts the damage these storms end up doing. We saw that especially in Katrina.

As a current example here in South Florida 2 heavily flooded areas in Palm Beach County, Wellington and the Acreage, are being impacted by environmental regulation laws created by politics that limit the amount of water that can be pumped out of these flooded communities each day.

The residents are furious and flipping out. Florida's Governor even came down here to help deal with the delays in getting the water pumped.


Yes but this blog is not about political affects on weather... its about weather... and weather solely... no political talk is accepted and if it is said it will be reported and most likely removed
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Quoting Dakster:


Are you back in Dade or still in Tally?


I'm back in Tallahassee for classes.
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Quoting fldude99:


2nd most prone area? By who's standards? Any area along the gulf coast, from Pensacola to Galveston, would beg to strongly disagree. South Florida has had a pass since Andrew. Wilma was a bad deal mostly due to the incredibly inferior infrastructure thanks to FL P&L. Pitiful really
This is what the NHC says:

NHC
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790. KRL
Quoting GeorgiaStormz:
EVERYBODY SHUT UP ABOUT POLITCS NOW


Actually POLITICS directly impacts the damage these storms end up doing. We saw that especially in Katrina.

As a current example here in South Florida 2 heavily flooded areas in Palm Beach County, Wellington and the Acreage, are being impacted by environmental regulation laws created by politics that limit the amount of water that can be pumped out of these flooded communities each day.

The residents are furious and flipping out. Florida's Governor even came down here to help deal with the delays in getting the water pumped.

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Quoting opal92nwf:
This reminds me of the initial models for Issac when it was about in this spot. Be wary that it might not go out to sea as quickly or at all as the models are pointing out.


will be another case of how weak it says imo
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72 Hours.
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106 for a high in Corpus Christi today.
Unreal for a coastal city, even by Texas standards.
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66 hours.
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Quoting Michfan:
GFS so far basically keeps Issac parked over LA for the next 24 hours. Not good.


Until there's something that shifts in that ridge to the N, there is literally _nowhere_ for isaac to go. I'd not be surprised to see him more or less just hang out there for the next 24 hours. I suspect all of the models will do the same.

At this point, we need to hope he starts to really fall apart, I think. Another 24 hours of this is going to be incredibly destructive.
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60 hours.
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Still getting hammered in Beloxi/Gulfport area. Live!
Member Since: August 17, 2005 Posts: 26 Comments: 16874


48 Hours.
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Quoting opal92nwf:
This reminds me of the initial models for Issac when it was about in this spot. Be wary that it might not go out to sea as quickly or at all as the models are pointing out.


I don't recall seeing a single model to indicate Isaac being a fish storm
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Quoting Articuno:
Dang, is this video REAL? :O



Category 1 winds lol??
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36 Hours:

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At 2pm





4:35 pm

Is this thing moving at all?!!?!
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Tropical Atl view. 24 hours.
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This reminds me of the initial models for Issac when it was about in this spot. Be wary that it might not go out to sea as quickly or at all as the models are pointing out.
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Quoting redwagon:

It's a shocking map, Centex atmo has been running precip away for so long (18 months) it's astonishing to see any map with any accumulation for us.


I've seen maps like that before...
There's a 20% chance for Saturday.
Otherwise nada
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Quoting GTcooliebai:
Weather Research and Forecasting Model (WRF)



If the color is QPE (quantitative precipitation estimate or model forecast precipitation) then WRF looks unrealistic for 98L. It develops it into a strong TS and looks like CAT 1 later, but the precip field is very asymmetric (and seems light as well) through its evolution. This affects both pressure and track in the model.
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GFS so far basically keeps Issac parked over LA for the next 24 hours. Not good.
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Quoting ElConando:


Wilma was the last official Hurricane to strike Fla. It's been 7 years. My area, NE Dade county averages a strike or near pass every 6 years. It's the second most Hurricane prone area (in the U.S.) according to statistics, first being the outer banks of North Carolina.


2nd most prone area? By who's standards? Any area along the gulf coast, from Pensacola to Galveston, would beg to strongly disagree. South Florida has had a pass since Andrew. Wilma was a bad deal mostly due to the incredibly inferior infrastructure thanks to FL P&L. Pitiful really
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Quoting dhcoop59:
It's hard to wade through the political crap to get info on affected areas. I have a friend that's desperately trying to get some info out of Slidell. Does anyone have a report from that area about conditions?
I have been trying to reach a friend of mine from over there all day both by land line and cell...no luck here.
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TCFA issued for 98L.

SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE
WITHIN 100 NM EITHER SIDE OF A LINE FROM 13.6N 37.6W TO 15.1N 45.7W
WITHIN THE NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT
IMAGERY AT 291830Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 13.5N 37.5W. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 20
KNOTS.
2. REMARKS: CURRENT MODEL GUIDANCE IS DEPICTING INTENSEIFICATION OF
A TROPICAL WAVE LOCATED ABOUT 700 MILES WEST-SOUTHWEST OF THE CAPE VERDE
ISLANDS. AT 291830Z, VISIBLE SATELLITE IMAGERY INDICATED AN AREA
OF MODERATE CONVECTION THAT HAS PERSISTED OVER THE LAST 24 HOURS.
WARM SEA SURFACE TEMPERATURES OF 80 TO 82 DEGREES FAHRENHEIT IN
CONJUNCTION WITH A FAVORABLE UPPER AIR ENVIRONMENT MAY ENHANCE
DEVELOPMENT OF THIS SYSTEM INTO A TROPICAL CYCLONE.
3. THIS ALERT WILL BE UPGRADED TO WARNING OR REISSUED AS REQUIRED
BY 301900Z.//

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Wow, watching the Weather Channel this whole time you would think we were having the weather equivalent of World War 3!!!!!!!!!!!!
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I can see the east side rain bandas and we just had another moderate squall pass through but winds are currently down significantly in mid New Orleans with light rain. Winds on my street on the high end of breeze.

Damage to this area is minimal, no street flooding, one bamboo cluster down. No significant limbs. Power back on in our immediate neighborhood. I guess the racetrack is an "essential facility".

Many other significant problems from WWL-AM: back flooding from the lake in LaPlace and water in Mandeville (north shore lake front, no levees, perennial problem with strong northerlies. Only lakefront gauge at New Basin Canal on the south shore near Orleans/Jefferson border shows tide at 6.3 feet (high tide Sunday 1.5 ft). So there is a lot of extra water in the Lake Pontchartrain driven west and north flooding LaPlace and the northshore.

There is a dusk-to-dawn curfew tonight. Good luck enforcing that in the French Quarter.

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Quoting Michfan:

barely moving
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Quoting Michfan:

oh no
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Quoting TropicalAnalystwx13:
Should go up to 70%/80% at the 8pm EDT TWO.


if it become leslie before friday, we will tie up with 2004 for most ts in august
theirs's was bonnie-jeanne i think
ours could be ernesto- leslie
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Quoting debrr:
Levee problems anywhere near Lake Okeechobee are of great concern, I would think. The Palm Beach County levee mentioned in a recent post is only a couple dozen miles from that massive TOXIC lake.

I don't know the condition of the levees before the rains, but a 1928 hurricane-induced breach of the levees killed 2,500 people and flooded hundreds of square miles.


The levee around Lake Okeechobee was massively rebuilt following the 1928
hurricane. The levees that existed around the lake prior to then were nothing at all like what was built there afterward, they were much smaller and far less well built.

The issues surrounding levees in the Lake Okeechobee area today have to do with the age of the structure(s) and the possibility that a catastrophic flooding event could cause the system to fail as a result. The same problem exists in many other areas around the country, including the Sacramento Valley area of California.

As for the lake being toxic, I think that situation is being slowly improved now as a result of recent efforts such as the Kissimmee River restoration project, for example. A few years back, US Sugar agreed to sell their massive properties to the west and south of the lake, in the Clewiston area, in order for the state and federal government to expand their Everglades restoration program. I believe that once that is all said and done the water quality in Lake Okeechobee will also be improved.
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Quoting mobilebayal:

Sheri, you stay safe!


I am, you to where are you located at? I hope stormsurgeon is ok, I think that's his name, I think he lives on Dauphin Island. They lost power last night sometime and there's no access to the Island.
this is really starting to worry me with all the flooding around here. Trees are gonna start up rooting out of the ground like when Georges hit us, I lost a apple,peach,pecan,walnut tree because of him.

Sheri
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Lake Pontchartrain level at Mandeville nears record level. At 4PM, level at 7.55,record level was 7.60 on 10/28/85-that would be Hurricane Juan

Link
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Quoting Michfan:


Problem is that the natural sedimentary cycle that made most of that land was ruined due to water being diverted to other areas upstream for irrigation, flood control, etc... No one ever thought to think of what this would do in the long run.


The Mississippi River Levee System also contributes quite a bit to the problem -- before the Army Corps built the Levees, the river would carry sediment, stirred up in floods, to the delta and replenish the geographic structures (and fertilize the land). Of course, that also meant that, for thousands of miles, farmers and communities along the river had to endure costly/dangerous floods.

MRGO also played a role in lower Mississippi delta land loss, as well.
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Should go up to 70%/80% at the 8pm EDT TWO.

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Quoting ElConando:


Wilma was the last official Hurricane to strike Fla. It's been 7 years. My area, NE Dade county averages a strike or near pass every 6 years. It's the second most Hurricane prone area according to statistics, first being the outer banks of North Carolina.


Are you back in Dade or still in Tally?
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Quoting TropicalAnalystwx13:
Hearing reports that a second levee has broke...this time on the north side of Lake Pontchartrain.
A second breach - different one from the one near Madisonville near Guste Island that shore and I mentioned earlier?

The winds now are sending more surge across Lake Pontchartrain from W to E toward the north shore and this will probably be enhanced as the storm moves more inland.

Also, wu blogger sarahjola is up that way, somewhere near Mandeville. Hope she's doing okay.

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You can see here how badly blocked Issac is and why he is moving so slow. There is just no way he is breaking through that. Its present at all levels of the atmosphere. Until that trough comes through hes basically stuck.
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750. CJ5
98L consolidating nicely. We could be surprised with a name tomorrow.
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Lakefront Airport 11:53 Light Snow Fog/Mist and Windy 80ºF 76ºF 87% E 51 G 64 29.14 in


I guess the snow is melting as it hits the ground. LOL
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Quoting Hurricanes305:


Carolinas and the gulf coast in general have been the targets for tropical system lately. I haven't had a hurricane in Florida since 2005 (pending on if Beryl is going to be upgraded this offseason) and especially South Florida.


Wilma was the last official Hurricane to strike Fla. It's been 7 years. My area, NE Dade county averages a strike or near pass every 6 years. It's the second most Hurricane prone area (in the U.S.) according to statistics, first being the outer banks of North Carolina.
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Quoting catastropheadjuster:
Hello everyone, I live in a town right outside of Mobile,Al called Satsuma it has rained and rained all day. Sometimes just a little and sometime pretty durn hard like right know, wind is blowing and can't even see across Hwy 43. All our creeks and bayou are out in the woods or in folks houses. I wanted to say folks be very careful with this because of gators and snakes. All the creepy crawlys. I hope Pat and everyone in Louisiana are ok. I have prayed for you all all day. God Bless you all.

Sheri

Sheri, you stay safe!
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Quoting hurricanehanna:
\
serious? Oy. We need to get Isaac outta here. Supposed to be between us and Baton Rouge around 7. Been having sustained winds around 35 with gusts up to 50 mph. Raining, but not bad. Really feeling bad for those to our East into Mississippi.


Yep! Unfortunately I don't think it is moving at all in my opinion. I'm just basing that on radar though. It is NW of where it was yesterday but not by much..
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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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