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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My thoughts. Please let me remind you that my forecast for Leslie is very low confidence.

Member Since: July 6, 2010 Posts: 113 Comments: 32024
Quoting GTcooliebai:
The Euro might be showing the remnants of Isaac redeveloping off the southeast coast, kind of like what Ivan did back in '04 and to top it off an interacting with Leslie.

Link or image please!
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where is jasoniscoolman these days? he was an interesting guy
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284. FOREX
Quoting opal92nwf:

I agree. And even if it does get picked up by the trough a little, it probably won't be as far East and North as the models are predicting.


My untrained eye sis showing a light WNW motion now. Maybe starting to feel the weakness.
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The Euro might be showing the remnants of Isaac redeveloping off the southeast coast, kind of like what Ivan did back in '04 and to top it off an interacting with Leslie.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting SouthDadeFish:
Three months ago, who would have thought this season would have been this busy through August? This is why I love tropical meteorology. We still have so much to learn!


One thing I've learned about Mother Nature is that I don't know anything.
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192 hrs. can I get me some Fujiwhara?

Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting Grothar:


Tricky storm. We have seen many storms initially take this track and switch. I had written early on that Isaac would move into the Caribbean and not take the Northern route, only because of the timing of the trough. In this case there are a number of features which could move it North. The weakness left behind by Kirk, and the remnants of Isaac being in place along the east coast. However, there still exists the possibility of Leslie missing them both and have the ridge build back stronger than expected, which would move her more west. This one looks like it is going to be a very strong and large storm sooner than they believe. In my personal blog I wrote on the 27th, I saw this one coming. The atmosphere was just right for a strong system.

I also give advice on the best way to wax a car, but we'll save that for another blog.


I usually leave it up to the "experts" on the board to determine where a storm may or may not go but for the life of me I don't see Leslie getting anywhere near the Caribbean.
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Quoting CaribBoy:


On which island do you live?
I actually live in the Tampa Bay area. See post 270, we were not too long ago in a drought.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
WOW more action to come. a very strong TW about to come off the african coast tomorrow. this already looks like 99L
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12z Euro 168 hrs.

Member Since: August 31, 2009 Posts: 0 Comments: 5628
ADT data supports an 80kt initial intensity for Kirk; I believe that's just about spot on for the time being.
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Three months ago, who would have thought this season would have been this busy through August? This is why I love tropical meteorology. We still have so much to learn!
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Quoting GTcooliebai:
Know the feeling man to watch the rains go north or south of you.


On which island do you live?
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I wonder if Houston is approaching dought conditions, yet. Seems like it's been a long time since we had measurable precip.
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272. FOREX
Quoting WxNerdVA:
Kirk:


Isaac:


Leslie:


Sorry if this was already posted, but it looks as though Leslie is starting to move ever so slowly WNW now.
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Quoting GTcooliebai:
Know the feeling man to watch the rains go north or south of you.



lol our area can use a break in rainfall, I was looking at some rain gauges around the Tampa Bay area. Some places have had over 40 inches of rain Since June first, many of us have had at least 30 inches since then. It's amazing to look back and remember how just back in May we were in one of worst dry season droughts in Central Florida in I think 10+ years or more.

Even now, it hasn't rain since Monday here, but water is STILL flowing out of open fields and and the drain ditches/ponds are still full to the brim. There are some open fields by my house where there are ducks and small fish in them and cat tails growing in them because they've been water logged for several weeks now lol.
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Latest on the Lake Tangipahoa dam situation. Engineers onsite believe that the dam is holding, but cannot be certain until they are on site (which is happening now). An intentional small breach in the dam is being made to relieve pressure on the dam. Evacuations are being called for in preparation of a worst case scenario. Officials don't want to have to move people out of the way at 2am in the morning.
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Quoting cajunkid:


Freshwater, sediment diversion from Mississippi River could build wetlands in Barataria Basin

Link

It works, (great I might add) but oyster fisheries are fighting it every step.

I believe, and some data might point to this after this hurricane season, the levees along the Mississippi River (south of New Orleans) made the surge funnel up into Plaquemines Parish.



Oh! +1000 is this works!
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266. JLPR2
Quoting stormpetrol:


Could that be an "eye feature" around 13.9N/45.2W


Nah
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Quoting cajunkid:


Freshwater, sediment diversion from Mississippi River could build wetlands in Barataria Basin

Link

It works, (great I might add) but oyster fisheries are fighting it every step.

I believe, and some data might point to this after this hurricane season, the levees along the Mississippi River (south of New Orleans) made the surge funnel up into Plaquemines Parish.



I believe in Houston they re-deposit their dredging sediment.
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Very little dry air, but lows like to follow lows. Look at the position of Kirk and Leslie.




At 48 hours, the ridge still does not look that strong and Leslie is much further North.

Member Since: July 17, 2009 Posts: 71 Comments: 26126
Quoting WxNerdVA:


But the season's a bust, right?



nop
Member Since: May 21, 2006 Posts: 5091 Comments: 115084
Quoting Grothar:


Tricky storm. We have seen many storms initially take this track and switch. I had written early on that Isaac would move into the Caribbean and not take the Northern route, only because of the timing of the trough. In this case there are a number of features which could move it North. The weakness left behind by Kirk, and the remnants of Isaac being in place along the east coast. However, there still exists the possibility of Leslie missing them both and have the ridge build back stronger than expected, which would move her more west. This one looks like it is going to be a very strong and large storm sooner than they believe. In my personal blog I wrote on the 27th, I saw this one coming. The atmosphere was just right for a strong system.

I also give advice on the best way to wax a car, but we'll save that for another blog.


Grothar, thanks for getting back to me. so there's a lot of thing up in the air with this one. The high if it comes back in strong the further she goes west,right?
sheri
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Could that be an "eye feature" around 13.9N/45.2W
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Listen Everybody, Saturated Leslie Is Entertaining us all...
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.
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Quoting jeffs713:

Uh... what stadium effect? I see an intermittent ragged eye. Consistent with a cat 1 or weak cat 2.
Look at this picture of Igor, the last storm with a stadium effect:

Now look at Kirk:
It seems like there is a small divot right around Kirk's eye. It's not as pronounced, though, due to Kirk's size
Member Since: August 1, 2012 Posts: 0 Comments: 436
Quoting NICycloneChaser:


1939 California Tropical Storm. Only on record TC to have made landfall on the US West coast.

Link
Don't forget 1858 San Diego Hurricane.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
OK we've had the "I" storm in my area of Louisiana. Now I'm watching for the "R" storm which is the one I dread the most. Hopefully Isaac is all we get. My area has had back to back storms 3 or 4 times in my life that I can remember.
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Quoting NICycloneChaser:


1939 California Tropical Storm. Only on record TC to have made landfall on the US West coast.

Link



Which, coincidentally, was the year the movie "Gone with the Wind" premiered. deja vu?
Member Since: July 17, 2009 Posts: 71 Comments: 26126
Quoting clwstmchasr:


Go to Crown Weather and read his post when 94L was just 250 west of the Cape Verde islands which is way east of where Leslie is now. He new then that the future Isaac was a threat. Read his post today. It is not the same setup as with Isaac. As I just mentioned, I would not rule out a turn back to the west when Leslie gets north of the islands. We have seen it before. With Leslie strengthening, a poleward bias is logical.


everything is a threat with Crownweather..

but to trust models out this far out when we just saw how the models kept moving the track of Issac and ended up in NO should not having anyone feeling confident in their tracks..

I will just be over here in the corner watching it unfold as I did with Issac..
Member Since: August 19, 2006 Posts: 13 Comments: 15286
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Quoting catastropheadjuster:


Hey Grothar, could Leslie be our 1-2 punch? Or you think it will be pulled up where kirk is and not amount to much?

sheri


Tricky storm. We have seen many storms initially take this track and switch. I had written early on that Isaac would move into the Caribbean and not take the Northern route, only because of the timing of the trough. In this case there are a number of features which could move it North. The weakness left behind by Kirk, and the remnants of Isaac being in place along the east coast. However, there still exists the possibility of Leslie missing them both and have the ridge build back stronger than expected, which would move her more west. This one looks like it is going to be a very strong and large storm sooner than they believe. In my personal blog I wrote on the 27th, I saw this one coming. The atmosphere was just right for a strong system.

I also give advice on the best way to wax a car, but we'll save that for another blog.
Member Since: July 17, 2009 Posts: 71 Comments: 26126
Quoting Thing342:
I don't think a TC has ever made landfall on the US west coast.


1939 California Tropical Storm. Only on record TC to have made landfall on the US West coast.

Link
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Quoting Tazmanian:



well i cant help it if you are working 12 hrs days


we cant help when ur such a jerk either taz. like the weather, its out of our control. im tired of u acting like the blog police when ur the one needing policing.
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Quoting jeffs713:

Uh... what stadium effect? I see an intermittent ragged eye. Consistent with a cat 1 or weak cat 2.


Doesn't look ragged to me. In fact it has cleared.
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Quoting Jedkins01:


lol,


Too bad a tropical cyclone with the name Kirk hasn't made landfall on the west coast of the U.S. ;)
I don't think a TC has ever made landfall on the US west coast.
Member Since: August 1, 2012 Posts: 0 Comments: 436
Not sure if anyone saw this, but long range GFS has a 1004 mb. system in the SW Caribbean. I guess the MJO is set to return by then.



Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting tropicfreak:
Zoom in and you can really get a good idea of the stadium effect of the eye. Not to mention you can see the overshooting cloud tops from the most recent convective bursts.

Kirk Visible Flash Loop

Uh... what stadium effect? I see an intermittent ragged eye. Consistent with a cat 1 or weak cat 2.
Member Since: August 3, 2008 Posts: 16 Comments: 5881
T.C.F.W.
12L/TC/L/CX
MARK
14.05N/44.70W
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Quoting CaribBoy:
Quite depressing :

AFTER LESLIE THERE WILL BE PERIODS OF DRY WEATHER AND THE TRADE
WINDS WILL RESUME LATER IN THE WEEK. BUT OVERALL THERE WILL BE
ONLY LIMITED SHOWER ACTIVITY DURING THE AFTERNOONS IN THE WEST AND
THE EARLY MORNINGS ON THE NORTHEAST COASTS. NO SIGNIFICANT
TROPICAL ACTIVITY IS FORESEEN DURING THE NEXT 10 DAYS FOR THE
LOCAL AREA.


Know the feeling man to watch the rains go north or south of you.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Kirk is such a tiny storm wish it woulda got its act together sooner... Wish it would drift west get bigger and spin for like 3 days in circle. Anyone remember Kyle from 2002 or 03? He did circles for like 10 days between the East Coast and Bermuda. The only storm I can remember giving us 3 different swells.
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Of course the models can flip flop, they do it a lot, but this looks like a pretty high confidence forecast to me.





I know they switched with Isaac, but this is a totally different storm... We'll keep an eye on it as we do with all of them but right now out to sea is the most likely scenario.
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Quoting clwstmchasr:


Don't know about a fish because it may threaten Bermuda. This is not the same as Isaac. At this point with Isaac is was a considerable threat to the Islands. All of the models want to curve Leslie north. Now having said that, I would not totally rule out it getting pushed back west when it gets north of the islands.


Yea, but Leslie will be a much more developed storm and will "feel" the weakness much more than Isaac did. Leslie will be more prone to turn and hopefully well before Bermuda is threatened.
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Zoom in and you can really get a good idea of the stadium effect of the eye. Not to mention you can see the overshooting cloud tops from the most recent convective bursts.

Kirk Visible Flash Loop
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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.