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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from Plaguemines parish..................
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Quoting LargoFl:
from the 10 am NHC.............SINCE ISAAC IS FORECAST TO MOVE SLOWLY OVER THE NEXT 24-36 HOURS...

THERE WILL BE A PROLONGED THREAT OF FLOODING FROM HEAVY RAINS OVER
THE NORTHERN GULF COAST AREA AND THE SOUTH-CENTRAL UNITED STATES.

NATIONAL OCEAN SERVICE TIDE GAGES INDICATE THAT STORM SURGE HEIGHTS
OF 6 TO 8 FEET ARE STILL OCCURRING ALONG PORTIONS OF THE COAST OF
SOUTHEASTERN LOUISIANA AND MISSISSIPPI. GIVEN THE LONG DURATION
OF ONSHORE FLOW IN THESE AREAS...WATER LEVELS ARE EXPECTED TO REMAIN
HIGH THROUGH TODAY.

A SPECIAL THANKS TO THE CREWS OF THE AIR FORCE RESERVE AND NOAA
HURRICANE HUNTERS WHO FLEW A TOTAL OF 34 HAZARDOUS MISSIONS INTO
ISAAC...WHICH RESULTED IN AN IMPRESSIVE TOTAL OF 95 CENTER FIXES.


FORECAST POSITIONS AND MAX WINDS

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

$$
FORECASTER STEWART

Very impressive running that many missions over a week's span. Their data was absolutely invaluable, and likely saved lives.
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Quoting LargoFl:
thanks for the info..you can just feel the strength of this storm huh..amazing


It is called Ft Bayou and empties into Biloxi Bay.

We lived on the Bayou about 3 miles upstream from that bridge during Katrina. Had about 6" of water in the house during Katrina even though we were at an elevation of 16 ft.
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from the 10 am NHC.............SINCE ISAAC IS FORECAST TO MOVE SLOWLY OVER THE NEXT 24-36 HOURS...

THERE WILL BE A PROLONGED THREAT OF FLOODING FROM HEAVY RAINS OVER
THE NORTHERN GULF COAST AREA AND THE SOUTH-CENTRAL UNITED STATES.

NATIONAL OCEAN SERVICE TIDE GAGES INDICATE THAT STORM SURGE HEIGHTS
OF 6 TO 8 FEET ARE STILL OCCURRING ALONG PORTIONS OF THE COAST OF
SOUTHEASTERN LOUISIANA AND MISSISSIPPI. GIVEN THE LONG DURATION
OF ONSHORE FLOW IN THESE AREAS...WATER LEVELS ARE EXPECTED TO REMAIN
HIGH THROUGH TODAY.

A SPECIAL THANKS TO THE CREWS OF THE AIR FORCE RESERVE AND NOAA
HURRICANE HUNTERS WHO FLEW A TOTAL OF 34 HAZARDOUS MISSIONS INTO
ISAAC...WHICH RESULTED IN AN IMPRESSIVE TOTAL OF 95 CENTER FIXES.

FORECAST POSITIONS AND MAX WINDS

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

$$
FORECASTER STEWART
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Quoting LargoFl:
Water rescues in Waveland right now, and everything south of I-10 around Diamondhead is impassible.


The I-10 exit at Diamond Head is right on the water. That overpass was completely flooded during Katrina
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Quoting USCGLT:

This location is on a bayou right by the bridge leaving Ocean Springs MS, it is probably 5 feet above sea level
thanks for the info..you can just feel the strength of this storm huh..amazing
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It's bad, and not to downplay it here, but so much worse for our neighbors in Louisiana! We thank everyone for their thoughts and prayers. A special Thank You for Portlight and their assistance!!
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Quoting LargoFl:
North of ocean springs Ms.

This location is on a bayou right by the bridge leaving Ocean Springs MS, it is probably 5 feet above sea level
Member Since: August 30, 2008 Posts: 0 Comments: 37
Big dog rescue going on in St. Bernard's parish, TWC.
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Quoting LAlurker:

You don't understand LA. We live to eat, not eat to live!
Well said!
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Water rescues in Waveland right now, and everything south of I-10 around Diamondhead is impassible.
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Quoting oceanspringsMS:


Last report I saw this morning had 522,000 foe LA MS, and AL combined. Most in LA.


Thank you. My husband is waiting for the call to head down to help with the power restoration efforts; relies on me to keep him updated re the situation.

Prayers being sent to all affected by Isaac. It's an ugly storm. :(

Thanks to all of you who post here - your info is generally better than what I find on TWC.
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Quoting Hurricane12:


I'm sure it's possible, but why would you want to be cooking in those conditions?

I would wait a bit for winds to die down unless you're in a dire situation where you don't have any food to eat.

You don't understand LA. We live to eat, not eat to live!
Member Since: July 24, 2008 Posts: 0 Comments: 156
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Quoting MisipiGrl:
Largo: Ken Combs pier is in Gulfport, MS
oh ok ty, my mistake..looks bad there huh
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81. auburn (Mod)
Quoting fireflymom:
http://www.stormjunkie.com/live.php

Thanks!
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Quoting LAlurker:
Really, fellow bloggers, I know that many of you are tired of Isaac after 2 weeks of postings, but this is still going on here in LA, a lot still happening, still classed as a Cat 1 by NHC. Can you please refrain from posting about invests and TDs that won't affect anyone for days, weeks, or never. Give Isaac another day or two. Thanks!


We're more than aware of the situation with Isaac, we all have been following it very closely and we are aware of how bad it is in Louisiana right now, but there are other systems out there to track. I've been watching and posting on Isaac BUT I have also been posting and tracking 98L and Kirk as tropical cyclone genesis simply fascinates me.
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Quoting MNhockeymama:
Do any of you know the current number of power outages being reported for the GOM? I'm trying to find it, but the websites are overloaded and running very slowly. TYIA


Last report I saw this morning had 522,000 for LA MS, and AL combined. Most in LA.
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Largo: Ken Combs pier is in Gulfport, MS
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Lafayette Parish including all municipalities will be under a curfew beginning at 6 p.m. Wednesday
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When levees fail water comes up very fast 1'-15' almost instantly. #Isaac



This is in line with the reports that came out of plaquemines parish
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Quoting TomballTXPride:
I hate to even say this, but their has be a jog to the NE and I want someone to convince me this is not the track. Many, at least, entertained this as a possibility last night.
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Quoting truecajun:
can you bbq on a charcoal weber in 30mph winds?
as long as your not standing in a puddle with a down power line in it. speaking of be careful all about stepping in puddles when you go out. a power line could be down a block away and if in the water can electrocute you.
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Please remember my friends at Back Bay Mission in Biloxi. Portlight does great work, but Back Bay Mission stays on the job helping folks recover for years after the hype and hoopla have faded.
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72. Skyepony (Mod)
The radioactive sinkhole has been sitting in the eyewall for quite some time.
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Do any of you know the current number of power outages being reported for the GOM? I'm trying to find it, but the websites are overloaded and running very slowly. TYIA
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Quoting dader:


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


It's psychology really. We humans are a reactive species, not a proactive species by nature. It's always going to happen. In everything we do. It's "close the barn door after the horse runs out."
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Biloxi pier..geez.....................
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http://www.stormjunkie.com/live.php
Quoting auburn:


do you have a link?

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Heavy band moving through Biloxi/Gulfport area now, training. Live feed!
Member Since: August 17, 2005 Posts: 26 Comments: 15666
66. auburn (Mod)
Quoting fireflymom:
They are just out side of Biloxi, Sorm junkie is live streaming to help raise funding.



do you have a link?
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Doc - Also the levees that overtopped were not Mississippi river levees, but levees that control water backed up from Lake Borgne (like Shell Beach) and Black Bay.
Member Since: July 24, 2008 Posts: 0 Comments: 156
Biloxi beach
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Quoting oceanspringsMS:


Katrina. The sustained wind here haven't been more than 30-35 mph, surge is 10-12 ft less,and still have power. Even the sat, TV is stil working
Cool. Hope it doesn't get worse. At least you have power still.
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Quoting E46Pilot:
Man, Isaac is just sitting there. I've always said a Cat 1 storm can be just as bad as a stronger storm. Especially when it just sits there like that. The surge is topping the levees. They are holding but if they are not high enough that can be just as bad. Praying that Isaac gets moving and gets out of there real fast. Yes we have had flooding here in Palm Beach county but it's nothing compared to what they are going trough. Can't even imagine having head high water in the house.


It's completely heart wrenching to see photos of people being saved from those parishes and cities that are currently flooded.
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Doc thanks for the update - but very little (basically only the rain that falls in the river itself and some from the Red river that doesn't drain through the Atchafalaya) of the rain that falls in LA drains into the Mississippi. We'll have to wait for rain that falls in MS west of the Pearl river basin and in states further north to flow into the Mississippi River.
Member Since: July 24, 2008 Posts: 0 Comments: 156
They are just out side of Biloxi, Sorm junkie is live streaming to help raise funding.
Quoting VAstorms:
Is Portlight heading to the Gulf coast? They are going to need help asap.

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Man, Isaac is just sitting there. I've always said a Cat 1 storm can be just as bad as a stronger storm. Especially when it just sits there like that. The surge is topping the levees. They are holding but if they are not high enough that can be just as bad. Praying that Isaac gets moving and gets out of there real fast. Yes we have had flooding here in Palm Beach county but it's nothing compared to what they are going trough. Can't even imagine having head high water in the house.
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Quoting Waltanater:
If there is anyone still blogging that has experienced both Katrina AND Isaac, please post your comparisons and contrasts between the two storms. Which one was worse, based on your experience of course. No more than 1,000 words please...LOL
Quoting Waltanater:
If there is anyone still blogging that has experienced both Katrina AND Isaac, please post your comparisons and contrasts between the two storms. Which one was worse, based on your experience of course. No more than 1,000 words please...LOL


Katrina. The sustained wind here haven't been more than 30-35 mph, surge is 10-12 ft less,and still have power. Even the sat, TV is stil working
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Quoting CocoaLove:
Anyone on here from Hattiesburg, Columbia, Collins area? My family lives in that vicinity. Please check in with what's happening if you can.


I'm in Hattie/Laurel area. Breezy, with some gusts, but not bad. Raining off and on. I think tonight and tomorrow will be worse in this area, but nothing like Katrina.
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Quoting CocoaLove:
Anyone on here from Hattiesburg, Columbia, Collins area? My family lives in that vicinity. Please check in with what's happening if you can.







I live just a little north of Columbia and its just a lot of rain and wind (about 25 to 30 mph with higher gusts). Here and we still have power so far. I hope it stays on.
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Quoting truecajun:
can you bbq on a charcoal weber in 30mph winds?


I'm sure it's possible, but why would you want to be cooking in those conditions?

I would wait a bit for winds to die down unless you're in a dire situation where you don't have any food to eat.
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inching slowly now next stop baton rouge by sundown then mcCoom by noon tomorrow for the eye

houma on the mark for the backside of the storm

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Is Portlight heading to the Gulf coast? They are going to need help asap.
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Quoting truecajun:
can you bbq on a charcoal weber in 30mph winds?



Yesssssssssssss u can.. not safe but it can be done jajajaja
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Crazy flooding just south of Slidell LA! Live video stream here:
Link

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Quoting LAlurker:
Really, fellow bloggers, I know that many of you are tired of Isaac after 2 weeks of postings, but this is still going on here in LA, a lot still happening, still classed as a Cat 1 by NHC. Can you please refrain from posting about invests and TDs that won't affect anyone for days, weeks, or never. Give Isaac another day or two. Thanks!
Amen-Some people do anything for Attention
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Quoting Waltanater:
Good post there! Thanks and hope you fair well.



We've done well so far, only 1/3 the way through though so...
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Quoting truecajun:
can you bbq on a charcoal weber in 30mph winds?


I know that you can on a Big Green Egg!
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A NASA satellite captured a spectacular photo of what is now Hurricane Isaac from space, a nighttime view showing the then-tropical storm's clouds lit up by moonlight as it approached the U.S. Gulf Coast.

NASA's Suomi-NPP weather tracking satellite recorded the amazing nighttime photo of Isaac just after midnight on Tuesday (Aug. 28). The bright city lights of New Orleans, Houston and Tampa, Fla., can be easily identified, but the photo also includes lights from cities all along the Gulf Coast, Florida and the southeast U.S. coast.

"The image was acquired just after local midnight by the VIIRS 'day-night band,' which detects light in a range of wavelengths from green to near-infrared and uses light intensification to enable the detection of dim signals," NASA officials explained in an image description. "In this case, the clouds of Isaac were lit by moonlight."




Link
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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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