Unanswered questions concerning Hurricane Isaac

By: Dr. Jeff Masters , 4:35 PM GMT on August 31, 2012

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The top winds of Tropical Depression Isaac have fallen to 25 mph, but the storm continues to be a potent rain-maker as it heads north-northwest at 11 mph into Missouri. Isaac has spawned up to 20 suspected tornadoes, brought storm surges as high as 13.6' to the coast (in Lake Borgne, LA), and dumped 20" of rain at one station in New Orleans. The 13.27" of rain that fell at Hattiesburg, MS broke the record for wettest August in the city's history (previous record: 13.03" in 1987.) Major flooding is occurring on seven rivers in Louisiana and Mississippi. Isaac is being blamed for at least four deaths in the U.S., 24 in Haiti, and five in the Dominican Republic.

A few notable rainfall totals from Isaac, through 11 am EDT on Friday:

20.08" New Orleans, LA
15.02" Marion, MS
13.99" Pascagoula, MS
13.27" Hattiesburg, MS
10.85" Gulfport, MS
10.39" Slidell, LA
10.17" Biloxi, MS
9.85" Mobile, AL
7.38" Pine Bluff, AR
5.95" Baton Rouge, LA

A major reason for Isaac's heavy rainfall totals has been its very slow motion. This slow speed was due to the fact Isaac has been bumping into a ridge of high pressure that is unusually strong, due to the intense drought over the center of the U.S.; strong drought-amplified high pressure areas are very resistant to allowing any low pressure areas to intrude into their domain. The high pressure area was strong enough this week to allow several all-time records for heat this late in the year to be set:

112° on August 29 at Winner, SD
108° on August 29 at Valentine, NE
107° on August 29 at Corpus Christi, TX
97° on August 29 at Denver, CO (2nd highest so late in the year)


Figure 1. Nighttime view of Hurricane Isaac taken at 1:57 am CDT August 29, 2012, by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-NPP satellite. The VIIRS day-night band detects light in a range of wavelengths from green to near-infrared, and uses light intensification to enable the detection of dim signals. In this case, the clouds of Isaac were lit by moonlight. Image credit: NASA.

Isaac's beneficial rains falling in drought-stricken regions
Hurricanes get a lot of attention because of the billions in damage they cost, and the lives they disrupt. AIR Worldwide estimated today that insured damage from Isaac would cost up to $2 billion. This does not include damage to infrastructure or uninsured damage, so the final price tag of Isaac's rampage will be more like $3 - $5 billion. However, Isaac is now dumping beneficial rains over Arkansas, Missouri, Illinois, Indiana, Ohio, and Kentucky--regions stricken by the worst drought since the 1950s or 1930s, depending upon the exact location. These regions need 9 - 18 inches of rain to pull them out of drought. Isaac's 3 - 6 inches of rain will not end the drought, but will put a pretty good dent in it. I expect that 3 - 6 inches of rain for a wide swath of prime agricultural land in extreme drought is probably worth at least $5 billion, when you consider that a recent estimate by a Purdue economist put the cost of the great drought of 2012 at more than $77 billion. Only Hurricane Katrina ($146 billion) and the drought of 1988 ($78 billion) have been more expensive disasters, according to NOAA's National Climatic Data Center. Unfortunately, Isaac's arrival is poorly timed, as the storm is arriving during harvest season. The strong winds associated with the storm will flatten many crops, making it more difficult to harvest them, and Isaac's winds may cost farmers several hundred million dollars due to unharvestable crops. Still, the rains from Isaac will be highly beneficial for the success of the upcoming winter wheat season, and for next year's growing season.


Figure 2. Predicted precipitation for the five-day period ending on Tuesday evening shows that Isaac is expected to bring a large region of 3 - 6 inches of rain (red, orange, and brown colors) to Arkansas, Missouri, Illinois, Indiana, Ohio, and Kentucky. Image credit: NOAA/HPC.


Figure 3. The great drought of 2012 has brought so little rain to the Midwest that some areas require over 15" of rain (dark purple colors) to end the drought. Image credit: NOAA/CPC.

Unanswered questions about Hurricane Isaac

1. Did the passage of Hurricane Isaac stir up oil from the Deepwater Horizon oil spill? Isaac was the first hurricane to pass over the site of the 2010 Deepwater Horizon oil spill. We know that large hurricanes are capable of creating currents in deep water at the bottom of the Gulf of Mexico; Hurricane Ivan caused upwelling currents of 0.5 cm/s at a depth of about 500 meters. In an August 28 article in the Huffington Post, Nick Shay, professor of meteorology and physical oceanography at the University of Miami, said: "Winds will push water away from the center of a storm, which causes an upwelling as the ocean tries to adjust. It brings whatever is near the bottom up higher in the water column and currents can then push it towards the coast." Up to 1 million barrels of oil from the spill are estimated to still be present in the deep water sediment, on beaches, and in the marshes of Louisiana, and it is possible some of this oil will wash up on the Gulf Coast in coming months. The storm surge of Isaac also likely flushed out oil lodged in the coastal marshes of Louisiana, but it is unknown how much of a concern this might be.

2. What's the deal with these super-sized Category 1 and 2 hurricanes that have been hitting the U.S.? The past three landfalling hurricanes in the U.S.--Isaac (2012), Irene (2011), and Ike (2008)--have all been exceptionally large, among the top ten on record for horizontal extent of tropical storm-force winds. Each of these storms had an unusually low pressure characteristic of a storm one full Saffir-Simpson category stronger. Is this the new normal for U.S. hurricanes?

3. Did the new $14.5 billion upgrade to the New Orleans levee system cause worse flooding elsewhere? Whenever a new levee or flood control structure is created, you make someone else's flood problem worse, since the water has to go somewhere. Where did the water was stopped by the new $1.1 billion, 1.8 mile-long Lake Borgne flood barrier on the east side of New Orleans go? Did it flow south and contribute to the overtopping of the levees near Braithwaite? Or did it go north and contribute to the 36 hours of storm surge in excess of 5' observed along the Mississippi coast at Waveland? I posed this question to NHC's storm surge expert Jaime Rhome, and he said it was impossible to know without doing detailed storm surge modeling studies.

4. Can only hurricanes beginning with the letter "I" hit the U.S. now? Isaac (2012), Irene (2011), and Ike (2008) are the last three hurricanes to hit the U.S. It turns out that hurricanes that begin with the letter "I" and "C" have more names on the list of retired hurricanes than any other letter (nine each.) I'm thinking Isaac will get its name retired, letting storms beginning with "I" take over sole possession of first place on the retired storms list.

Hurricane Kirk in the Central Atlantic
Hurricane Kirk intensified into a 105 mph Category 2 hurricane this morning, becoming the 2nd strongest hurricane of the 2012 Atlantic hurricane season. Hurricane Gordon was the only stronger storm; Gordon hit sustained winds of 110 mph just before reaching the Azores Islands on August 18. Kirk has probably peaked in intensity, and is about to move over colder waters and gradually decay. Kirk is not a threat to any land areas.


Figure 4. Morning satellite image of Tropical Storm Leslie.

Tropical Storm Leslie a long-range threat to Bermuda, Canada, and the U.S. East Coast
Tropical Storm Leslie formed on Thursday in the Central Atlantic. Leslie's formation date of August 30 puts 2012 in 2nd place for earliest formation date of the season's 12th tropical 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. Satellite loops show that Leslie has a modest amount of heavy thunderstorm activity, and respectable low-level spiral bands and upper-level outflow. Conditions appear ripe to allow Leslie to intensify into a Category 2 hurricane by Sunday. 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. However, steering currents for Leslie are expected to collapse early next week, as Leslie gets stuck between two upper level lows. The storm will then slowly meander over the open ocean for many days, potentially threatening Bermuda. Leslie will stay stuck until a strong trough of low pressure approaches the U.S. East Coast around September 8. This trough should be strong enough to pull Leslie to the north and then northeast by September 9. At that time, Leslie may be close enough to the coast that the storm will make landfall in New England, Canada, or the Mid-Atlantic states. Leslie could also miss land entirely; this all depends upon the timing and strength of the September 8 trough of low pressure. Regardless, Leslie is expected to bring an extended period of high waves to the U.S. coast. According to NOAA's Wavewatch III model, large swells from Leslie will reach Bermuda by Monday, and arrive along the U.S. East Coast on Tuesday. These waves will be capable of creating dangerous rip currents and beach erosion.

Portlight disaster relief charity responds to Isaac
The Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, are in Mississippi, helping out with Isaac relief efforts. You can check out their progress or donate to Portlight's disaster relief fund at the portlight.org website.

I'm planning on taking Saturday off, but will have a new post for you on Sunday. Have a great holiday weekend, everyone!

Jeff Masters

Hurricane Isaac Louisiana (apphotos)
People play in the storm surge from Hurricane Isaac, on Lakeshore Drive along Lake Pontchartrain, as the storm nears land, in New Orleans, Tuesday, Aug. 28, 2012. (AP Photo/Gerald Herbert)
Hurricane Isaac Louisiana
Portlight volunteers at Biloxi shelter (Portlight)
Portlight volunteers at Biloxi shelter
Hurricane Isaac Louisiana (apphotos)
Research students from the the University of Alabama measure wind speeds as Hurricane Isaac makes landfall, Wednesday, Aug. 29, 2012, in New Orleans, La. Isaac was packing 80 mph winds, making it a Category 1 hurricane. It came ashore early Tuesday near the mouth of the Mississippi River, driving a wall of water nearly 11 feet high inland and soaking a neck of land that stretches into the Gulf. The storm stalled for several hours before resuming a slow trek inland, and forecasters said that was
Hurricane Isaac Louisiana
TS Isaac (Raine911)
Between the rain bands
TS Isaac

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Leslie satellite imagery shows that the mid level circulation is not aligned with the low level circulation. There is a displacement between circulations and convection is not over the LLC the way it needs to be to strengthen into a hurricane.
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Quoting Slamguitar:
I'm starting to get some upper level clouds associated with post-tropical depression Isaac here at my new home smack in the middle of the mitten. I think that's how we refer to him now... I wouldn't call that remnants. Too organized still.

I'm starting to get clouds and I'm on the east part of the mitten. Very few but they are from Isaac.
Member Since: March 16, 2012 Posts: 127 Comments: 7975
Well, I'm back.

My God did it rain so much.

We lost power a third time, and it rained about twice as much afterwards as before.

We got somewhere between 14.5 and 16.5 inches of rain (we lost track of it because the gauge filled up over night on the night before last).

Yellow Water Creek between Ponchatoula and Springfield has somehow managed to Crest about 4 or 5 FEET above the previous record.

Natalbany is somewhere near the previous record from 1983, but I'm not sure.

I must say, if this had been a true cateagory 2 at the same size, the people about a mile south east of me would have all died in their homes and apartments, or at least been forced onto the roofs.



I think NHC/NWS, army core, USGS, LSU, and Louisana state governemnt; whoever is responsible for the flood maps and storm surge models in this area needs to take a look at these scenarios, because this is worse than I imaged.

I thought this area was safe from anything less than a cat 4 or cat 5, and apparently it's not safe even from a large 2 or a normal 3 on THIS particular track.

People who have lived in this exact road for 50 to 75 years have never seen yellow water creek that high, not even in the 1983 flood....

We did not take water in our house or anythign within sight of our house, but if there had been another 5 feet of surge, like with a full cat 2 this size, we probably would have, and like I said, the people behind us by a mile to the SE would have all died in their sleep.

This is only a cat 5 evac zone and it may need to be a cat 2 or 3 evac zone...
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48 hours of high resolution radar from New Orleans.

Member Since: July 6, 2010 Posts: 113 Comments: 33144
Quoting ncstorm:


yeah and not knowing which direction they are supposed to go..
Men have always been good when it comes to strength but women have always had the smarts.Lol.
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Quoting VR46L:


But its a female storm Leslie .... cant see him when he was alive dancing with Kirk Douglas ...

anyways Kirk in rainbow


Kirk almost looks like he's spinning like he's on the other hemisphere. o_o or is it just my eyes playing tricks?
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Quoting SouthDadeFish:
Wonder what?

I...have no idea.
Member Since: July 6, 2010 Posts: 113 Comments: 33144
415. VR46L
Quoting mati:


Lol Leslie Nielson would have danced with a dog let alone Kirk Douglas!!!, a great comedic self depricating person as ever lived.


Yes but would Kirk Douglas have danced with him?


Anyway

Kirk and Leslie looking like they want to waltz in Rainbow



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Finally getting some rain in Montgomery County, IL. Radar made it look like we've had several bands since a.m., but this is first to actually amount to anything. Under tornado watch until 10, but never any heavy wind, though were some warnings to our west - radar indicated, haven't heard of any actual touchdowns. I guess he's supposed to turn soon, we have rain in forecast until Sunday evening. Hope central MO is getting a lot out of this, they really needed it badly.
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Quoting washingtonian115:
Leslie has the chance of becoming the first female name this year to attain hurricane status.The men have been in charge this year.


yeah and not knowing which direction they are supposed to go..
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Quoting TropicalAnalystwx13:
Makes you wonder.

Wonder what?
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Leslie has the chance of becoming the first female name this year to attain hurricane status.The men have been in charge this year.
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Those who think a disaster is a boost to the economy are perpetuating Bastiat's Broken Window Fallacy. Yes, there is economic benefit to those who are involved in providing the goods and services needed for repair, but the repairs and costs are not a net benefit to the economy because the money spent will not be spent on other things. See:

http://mises.org/daily/5593/The-BrokenWindow-Falla cy


Quoting kwgirl:
Exactly, it moves money around. While purchasing locally doesn't help the GNP it certainly helps the business man who has invested in inventory, who can now let his wife go to market to purchase their food, or buy new clothes. What has hurt our economy is the fact that we have just about stopped producing anything to sell other than weapons and cars. No, the disasters will not help with the national debt, in fact, they increase it. I am talking local, regional economies. Micro not Macro.
Link
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Makes you wonder.

Member Since: July 6, 2010 Posts: 113 Comments: 33144
Quoting washingtonian115:
Fabian comes to mind from 2003.I think Leslie will be a hurricane tonight.
I say 70mph at the 11pm update but imo should be a cat 1.
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Some remarkably deep convection firing, especially considering it is diurnal minimum:



Cloud tops well cooler than -80C!
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I'm starting to get some upper level clouds associated with post-tropical depression Isaac here at my new home smack in the middle of the mitten. I think that's how we refer to him now... I wouldn't call that remnants. Too organized still.
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Quoting wxgeek723:
Leslie better not pull something like this.


That was the last storm to make landfall as a hurricane here in NJ.
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Quoting Felix2007:




Good ones.They all had Bermuda in their sights.
Quoting BVI:


Here in the British Virgin islands and we are watching closely, weather is gorgeous right now
Dry air out ahead of the system is causing that.
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Leslie better not pull something like this.
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401. BVI
Quoting washingtonian115:
It's the 4Qing living dead on right now.

Any who if I was in the Antillies and saw what was coming from the east I don't i'll be a little freaked out.I don't know how those people can do it.


Here in the British Virgin islands and we are watching closely, weather is gorgeous right now
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Fabian comes to mind from 2003.I think Leslie will be a hurricane tonight.
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Quoting air360:
Anyone heard from Levi past few days? He hasn't updated his tropical tidbits since Wednesday - curious his thoughts on Leslie


From Levi's page

Watching Leslie closely as Bermuda could be directly in her path. The pattern has her likely missing one trough and slowing down south of the island before getting drawn into the next trough. The ECMWF has Leslie sitting south of Bermuda and strengthening for a few days before taking a close swipe at the island.

One can see the next storm west of Africa and an interesting trough-split feature near the Bahamas as well by Day 9. The tropics remain very active as we continue through the peak ...
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Quoting washingtonian115:
Never mind.Thinking of a completely different system.


oops :)
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It's the 4Qing living dead on right now.

Any who if I was in the Antillies and saw what was coming from the east I know i'll be a little freaked out.I don't know how those people can do it.
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RAW T# on Leslie have jumped to 4.4
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Looks like leslie is just a tad west of her forecast points, imo.
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Quoting catastropheadjuster:
So from what I'm reading we don't have anything to worry about with kirk or Leslie right? That's a good thing that nothing with get in the Caribbean or GOM for a while. Can't believe it's already Labor Day weekend. And no storms to worry with.

Sheri


Maybe not tomorrow or Monday - but I sure would keep a watch on the tropics and what is happening. Nothing is certain until after it happens - I've learned my lesson!!
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Quoting catastropheadjuster:
So from what I'm reading we don't have anything to worry about with kirk or Leslie right? That's a good thing that nothing with get in the Caribbean or GOM for a while. Can't believe it's already Labor Day weekend. And no storms to worry with.

Sheri
I'm not to convinced about Leslie yet until I know she is safely away from us hear on the east coast.In terms of you Gulfer's You all won't have to worry about these two storms.
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Quoting seer2012:
How much longer is Leslie going to continue mostly west before she starts ot make the turn?



has long has he wants two
Member Since: May 21, 2006 Posts: 5091 Comments: 115518
So from what I'm reading we don't have anything to worry about with kirk or Leslie right? That's a good thing that nothing with get in the Caribbean or GOM for a while. Can't believe it's already Labor Day weekend. And no storms to worry with.

Sheri
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Quoting Charmeck:


Sure does look like a eye is forming in Leslie!
It does. IDK if it is but if that is an eye she is not as far north as the NHC places her.
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How much longer is Leslie going to continue mostly west before she starts ot make the turn?
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Never mind.Thinking of a completely different system.
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Base on what Levi said in his page we could have Michael and Nadine by day 9 one by trough split and the other from an African wave.
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386. CJ5
Leslie looks good. Unlike Isaac, she has been a steady grower and it appears she will continue to get better. Let's hope she doesn't visit anyone on land.
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Sure does look like an eye is forming just below 15N in Leslie! Not where they say she is????
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Leslie appears bouncing along westward just above the 16N latitude line.

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"They kept saying Earl would turn."But he never did and someones labor day plans were ruined!".I remember seeing this on a broadcast two years ago.I can't seem to find it.But the family sounded awfully pissed they had to leave and head back after traveling 9 hours all the way to N.C for their vacation.We here on the east coast need a break after being the target for sometime now.
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Quoting Tazmanian:



no Leslie dos not want too obey orders

I hope you're not right. I don't want any surprises in PR this weekend.
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@post 357... Wow...DRYYYYYY!!!
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How far is Leslie from the islands?
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Quoting washingtonian115:
Looking good Leslie.Now obey orders and turn north please..



no Leslie dos not want too obey orders
Member Since: May 21, 2006 Posts: 5091 Comments: 115518
What if that was an actual eye? Lol.

Member Since: July 6, 2010 Posts: 113 Comments: 33144
Quoting air360:
Anyone heard from Levi past few days? He hasn't updated his tropical tidbits since Wednesday - curious his thoughts on Leslie

Not sure if you have a facebook, but he makes posts on his site page almost everyday.
Member Since: July 6, 2010 Posts: 113 Comments: 33144
Looking good Leslie.Now obey orders and turn north please..
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Leslie.... "Dancing Away the Great Depression"

: )
Member Since: July 12, 2007 Posts: 0 Comments: 6069
I think I see the eye of Leslie! Just kidding lol!! Hmmmm.... where is the center anyway??? Is this storm vertically tilted to the northeast or something?? Is the low level circulation in the midle of the blob and the mid and upper circulation located where the bright red blob are are to the northeast?? This could be a problem for the models to handle, but then again they alredy have enough problems to begin with. It would be a much bigger problem for the Islands.
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Quoting air360:
Anyone heard from Levi past few days? He hasn't updated his tropical tidbits since Wednesday - curious his thoughts on Leslie


I'm pretty sure his new school year at college just started so he might be slower to update for a while.
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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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