Gulf of Mexico disturbance 93L a Lousiana flood threat; Katia a hurricane

By: Dr. Jeff Masters , 3:28 PM GMT on September 01, 2011

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Surface winds over the northern Gulf of Mexico are rising, pressures are falling, and heavy thunderstorms are building today thanks to a tropical disturbance (Invest 93L) that is the product of a tropical wave interacting with an upper-level low pressure system. At 8:35 am CDT, winds at the Mississippi Canyon 711 oil rig were south-southeast at 38 mph. This is just 1 mph below tropical storm force, but the wind instrument was 348 feet (106 m) above the ocean surface, and winds near the surface were probably considerably lower, near 30 mph. Long range radar out of Mobile, Alabama shows heavy rain showers building along the northern Gulf Coast, but these rain showers are not organized into spiral bands and show no signs of rotation. Strong upper-level winds out of the west-northwest are creating 30 knots of wind shear over 93L, keeping the storm's heavy thunderstorms disorganized. Strong onshore winds raising tides to 1 - 2 feet above normal are likely along the northern Gulf Coast through the weekend, and coastal flood statements have been issued for the region.


Figure 1. Predicted rainfall for the 5-day period ending at 8am EDT Sep 6, 2011. A large region of rains in excess of 15 inches is expected over Southeast Louisiana. Image credit: NOAA/HPC.


Figure 2. U.S. drought conditions on August 30. The rains from 93L have the potential to bring major drought relief to drought-stricken portions of the coast. Image Credit: U.S. Drought Monitor.

By late tonight, wind shear is expected to drop to the moderate range, below 20 knots, and 93L should begin to organize into a tropical depression. Wind shear is expected to remain moderate, 10 - 20 knots, into Monday. There is some cold, dry air aloft that will retard this process, and I think the earliest we would see a tropical depression is Friday afternoon. NHC is giving 93L a 70% chance of developing into a tropical depression by Saturday morning. All of the major models develop 93L near the Louisiana coast, and show a slow and erratic movement due to weak steering currents. Coastal Louisiana, Mississippi, Alabama, and the extreme western Panhandle of Florida will likely receive very heavy flooding rains beginning this afternoon and intensifying Friday and Saturday. The latest rainfall forecast from NOAA Hydrological Prediction Center (Figure 1) shows that a large area of 15+ inches of rain is expected over Southeast Louisiana. The region is under moderate drought, so flooding problems will be delayed compared to what we'd normally expect from heavy rains of over a foot. Nevertheless, minor to moderate freshwater flooding is likely from 93L, and flash flood watches are posted for New Orleans and surrounding areas, and rainfall amounts of 1 - 3 inches per hour are possible in some of the heavier rain squalls. Ocean temperatures are near record warmth, 88°F (31.3°C), which will provide plenty of moisture for heavy rains, and plenty of energy to help 93L strengthen into a tropical storm. Most of the models predict 93L will have some motion to the west by Saturday, which would bring rains to the Texas coast near the Louisiana border. Steering currents will be weak in the Gulf this weekend and early next week, making it difficult to predict where the storm might go. If 93L stays over water through Tuesday, like the ECMWF model is predicting, the storm would be a threat to intensify into a hurricane. Most of the other models predict 93L will move ashore over Louisiana by Sunday, limiting the storm's development to just tropical storm strength. I think it at least 50% likely 93L will be a tropical storm with 40 - 60 mph winds along the coast of Louisiana by Sunday.

Hurricane Katia
Hurricane Katia intensified into the 2nd hurricane of the 2011 season last night, and continues its long trek across the Atlantic Ocean today. Katia is expected to arrive at a position several hundred miles north of the Northern Lesser Antilles Islands by Monday. The islands are not in the cone of uncertainty, and it appears unlikely that they will receive tropical storm-force winds from Katia. Satellite images show that Katia is a well-organized storm with plenty of heavy thunderstorms, but the storm has been struggling with dry air and moderate wind shear of 10 -20 knots, and is looking less organized than it did last night. These problems will likely diminish by Friday night, as the upper low bringing the wind shear moves away. It is still unclear how much of a threat Katia may post to the U.S. Dr. Bob Hart's Historical Tropical Cyclone Probability web page suggests shows that tropical storms in Katia's current position have an 16% chance of hitting North Carolina, a 21% chance of hitting Canada, a 12% chance of hitting Florida, and a 54% chance of never hitting land. I suspect that Katia will turn north before reaching the U.S. and potentially threaten Bermuda and Canada, based on what past storms in similar situations have done, and assuming the jet stream maintains its current pattern of bringing frequent troughs of low pressure off the coast of the U.S. It will be another day or two before the models will begin to have a handle on the long-term fate of Katia, though.


Figure 3. Morning satellite image of Katia.

94L
A well-organized low pressure system with a surface circulation and limited heavy thunderstorm activity has developed between Bermuda and the Canadian Maritimes. This disturbance, (94L), is headed out to sea, and is being given a 10% chance of developing into a tropical depression by NHC. 94L is under a very high 30 - 40 knots of wind shear, and will not be able to intensify very much. However, Tropical Storm Jose formed from a similar type of system, and we might get surprised by 94L.

I'll have more on Irene in tomorrow's post.

Jeff Masters

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Quoting twincomanche:
+1 for the second time today. These people do a great job and we should be cheering for them not criticizing. Set up your own gig here for a year and see how you do against their record.

True that. It's human nature to play armchair quarterback from the comfort of your anonymous WU handle, I suppose; it's safe, and fun to some. But those senior forecasters at the NHC have to actually put their name--and their reputation--on all the pieces of data that could affect hundreds of thousands of people and billions in assets. The pressure must be unimaginable at times...
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I'd be surprised if we weren't all banned by tomorrow morning, lol.

I'm out for the night guys, carry out the pointless argument about the argument, so Thunderpig can argue about the argument over the argument, and so on. I'll be on before school tomorrow to see how the tropics are doing, and also to see if the argument over the argument over the argument quit.

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Quoting WhoDat1:


agree, lapalco blvd starts holding water in a light shower, it dosnt take much to start flooding..


No one realizes how vulnerable the westbank is. I am not saying you dont of course.
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Quoting twincomanche:
+1 for the second time today. These people do a great job and we should be cheering for them not criticizing. Set up your own gig here for a year and see how you do against their record.


this and +2
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am not sure if any one say this but this is not good


2380. mrpuertorico 6:45 PM PDT on September 01, 2011 0 Hide this comment.
AFTER KATIA CLEARS THE AREA EARLY NEXT WEEK...MODELS SHOW A
SIGNIFICANT CHANGE TO THE UPPER LEVEL PATTERN WITH TUTTS/TROUGH
THAT ARE CURRENTLY PRESENT ACROSS THE ATLC TO BE REPLACED BY A
STRONG RIDGE ALOFT. THIS WILL BLOCK ANY POTENTIAL TROPICAL
CYCLONES ORIGINATING IN THE TROPICAL ATLC FROM TAKING THE NORTHERN
ROUTE. WHILE WE ARE MORE THAN LIKELY TO DODGE THE BULLET WITH
KATIA THIS MAY NOT BE THE CASE FOR FUTURE STORMS IN THE NEXT 7-14
DAYS.
Member Since: May 21, 2006 Posts: 5091 Comments: 115107
2586. scott39
Quoting nash28:


This will be a giant rainmaker. Most likely not a hurricane like so many in here are fretting over. This isn't going to be a Katrina. Ever since 2005, everything in the Gulf is being overblown into an apocolyptic storm that will wipe three states off the Atlas. Too much hype. It isn't gonna be the winds. It will be the water.
Thanks, but when is the wind shear going to relax over the center?
Member Since: June 13, 2009 Posts: 0 Comments: 6780
Quoting Thunderpig75:
Why is it that for the past 3 pages the only people I see arguing about the classification of this storm are the ones telling everyone to stop arguing about the classification of the storm.

Everyone stop arguing about the arguing of the classification of the storm. The initial arguing has subsided at this point and has spawned arguing about the arguing. If there are any more arguing tangents created about this we will have to resort to a knock down, drag out fight in order to prevent an infinite loop of arguing.


For some unknown reason, reading that makes me LOL.
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2584. DFWjc
Quoting TropicalAnalystwx13:

mhm...Why don't you tell that to some other people? ;)

Completely unnecessary.


well there is a difference between shut up(please quiet up), and then there's shut the eff up (shut the front door) sometimes you just gotta be blunt...LOL
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slackin off



vorticity is a go



mimic tpw is a go on the last few frames its a go



moisture is a go


Leggo clear for launch houston
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2582. scott39
Quoting Orcasystems:


Now thats Funny!!
Member Since: June 13, 2009 Posts: 0 Comments: 6780
Why is it that for the past 3 pages the only people I see arguing about the classification of this storm are the ones telling everyone to stop arguing about the classification of the storm.

Everyone stop arguing about the arguing of the classification of the storm. The initial arguing has subsided at this point and has spawned arguing about the arguing. If there are any more arguing tangents created about this we will have to resort to a knock down, drag out fight in order to prevent an infinite loop of arguing.
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2580. viman
Quoting kmanislander:


After 55 W

Kman, night, why do you think the northern islands are not in the clear, all indicators are saying north of the islands and it seems pretty high in latitude already?? TIA
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2579. nash28
Quoting scott39:
When is the shear going to relax over TD 13 center? I also saw on the last NHC discussion that the center could relocate.


This will be a giant rainmaker. Most likely not a hurricane like so many in here are fretting over. This isn't going to be a Katrina. Ever since 2005, everything in the Gulf is being overblown into an apocolyptic storm that will wipe three states off the Atlas. Too much hype. It isn't gonna be the winds. It will be the water.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
Quoting TropicalAnalystwx13:
This is why people can't have civilized discussions...People get carried away with their opinions (almost guilty, lol) and start calling people names and telling to shut up (*cough Dennis8 *cough).


I have already told him to shut up by putting him on ignore.
Member Since: July 15, 2006 Posts: 17 Comments: 10248
2577. ncstorm
KATIA

Member Since: August 19, 2006 Posts: 13 Comments: 15299
2576. Delsol
Quoting kmanislander:


After 55 W


Thanks!
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This is why people can't have civilized discussions...People get carried away with their opinions (almost guilty, lol) and start calling people names and telling to shut up (*cough Dennis8 *cough).
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2573. scott39
Quoting SuperYooper:


I'm pretty sure San Diego means a whales vagina though.
I will Agree to disagree.
Member Since: June 13, 2009 Posts: 0 Comments: 6780
Quoting P451:


I love how they mention "SATELLITE".

One look at any satellite image of this would make you laugh at the upgrade. But that's just a line they always use when typing up these reports.


So if this is a TD then what was 94L today? What was the previous invest in the same location while Gert was south of Bermuda? What was the system that moved across the BOC into Mexico?

The answer would be: Tropical Cyclones.


So, you see, it's not so much about TD13 being prematurely named, or the stretching of the rules to name it, it's about systems they decide to hold to strict rules that then go unnamed.

Seems to me it's become a make the rules on the fly situation.

That is not what I would expect from an official entity would you?




This blog moves too fast! LOL, I tried to follow-up. Could it be because they never got a chance to fly HH into those other systems, or possibly just didn't have the other 2 sets of data beyond just satellite presentation? Here, they used all three, with one not looking so hot, but based on the partial 'look' along with the HH and surface data, they had enough to overrule the satellite view? Simply speculating and trying to analyze their thinking.
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2568. help4u
Post 2558,lol!
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2567. xcool
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2565. DFWjc
Quoting nolacane2009:


I will def have to try that route then. Lol.


just explain to them why it benefits them... I never rose my voice, and I said look if you won't fix it, I'll go to Home Depot and put my own cones up and fill it will quickcrete and direct the traffic myself for the 60 minutes it will take it to fix the hole problem or we could try it my way and use the money for other projects in town...
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Quoting scott39:
Agree to disagree and move on please.


I'm pretty sure San Diego means a whales vagina though.
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2562. KEEPEROFTHEGATE (Mod)
or DDC
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All I can say is that the COC has a very high chance of being relocated more to the SE or to the E where the burst of convection is happening.
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Quoting Dennis8:


When I say shut up I use the words SHUT THE ^*&&)_)_ UP

mhm...Why don't you tell that to some other people? ;)

Completely unnecessary.
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Quoting Delsol:
When should we expect HH missions into Katia?


After 55 W
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Quoting P451:


Yes.

But the question is would you have classified it?

Does their classifying it sit well with you?

Do you feel they stretched their own rules to rush to classify it?

If you believe it deserves classification does it not sit well with you to know other systems that match this same criteria have been left unclassified?


See, one thing I look to in an official entity is continuity. Tonight is an example of a break in that continuity to me.

And that simply does not sit well with me.


The storm, location, what it will and won't do, is inconsequential to the debate in my opinion.





I honestly am rather disappointed that they classified it. The low center is BARELY defined on sattlite and ascat respectively and it is very hard to tell where exactly it is let alone which direction it is moving. Best guess is that its somewhere north and east of the main convection. But its quite possible that this is not the dominant center and in fact a new circulation is forming under the main area of convection.


Really no idea where this thing is going or what it will do at this point, for all we know it could easily disappate in 24 hours.
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2557. scott39
When is the shear going to relax over TD 13 center? I also saw on the last NHC discussion that the center could relocate.
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2556. KEEPEROFTHEGATE (Mod)
Quoting ImitationDorito:


What's up with those coordinates?
thats where they are going possible drop dead centre
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Quoting P451:


Yes.

But the question is would you have classified it?

Does their classifying it sit well with you?

Do you feel they stretched their own rules to rush to classify it?

If you believe it deserves classification does it not sit well with you to know other systems that match this same criteria have been left unclassified?


See, one thing I look to in an official entity is continuity. Tonight is an example of a break in that continuity to me.

And that simply does not sit well with me.


The storm, location, what it will and won't do, is inconsequential to the debate in my opinion.




It would NOT sit well with me if they didn't classify an ACTUAL tropical cyclone. What's the big deal of not feeling comfortable with them classifying a very much border-line system that's going to be a tropical storm in the next 24 hours? To me, I'd much rather have them classify a border-line system, rather than have them sit back and be passive. It's really not even a question.
Member Since: July 15, 2006 Posts: 17 Comments: 10248
If I earned a dollar every time someone here complained that the NHC had classified a storm they shouldn't have, I'd be a wealthy man. But if I had to pay a dollar every time someone here complained that the NHC had not classified a storm they should have--well, I guess I'd be back where I started. ;-)

Until and unless someone on this site can prove that they have even one-tenth as much education, knowledge, experience, wisdom, professionalism, and responsibility as the least senior person at the NHC where tropical weather is concerned, accusing anyone there of foul play is really just pointless and unfair sniping.
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Quoting DFWjc:


Glad i'm not there, i'd be all over city council... We've had a pot hole cause by running water for 6 months now and i told them i could save the city $2800/month if they would arch the black top so the water wouldn't run over and "wash" it out..sure enough they did that and no more potholes. Maybe your city government should hear a word from you....


Thanks for the tips DFW but ya gotta remember your dealing with sensible politicians up your way...waait a minute...sensible politicians?? Thats an oxymoron isnt't it?
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Just wondering if anyone with good knowledge base think there is a likelihood of the LLC of TD13 developing under the heavier convection to the SE of where the NHC placed the LLC earlier?
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Quoting DFWjc:


like i said, it took me 6 months...the look on the council's faces every month when i came to the podium to speak... for a hole no bigger than 2 DVD cases...


I will def have to try that route then. Lol.
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Quoting NOLALawyer:
Enough bickering over classification with this storm. It is over the Gulf, with smoking hot water. There are hundreds of oil rigs beneath it, there are cities full of people just North of it...cities that are prone to flooding. Do not forget that the NHC sometimes has to make a political decision. This may be one of those times. This is sitting below me, so I am grateful for the NHC's actions. I am very concerned about flooding this weekend.


Man I tried to say that one time... that sometimes there's a political and public interest metric to some of NHC's statements... and I got nuked.

I think it was a good call.
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Quoting kmanislander:


Not a signature one would have expected from a system that was a hurricane this morning. No classic closed center.

The Northern Leewards need to pay attention to this, as does the central Bahamas IMO


I agree. A similar situation happened when Andrew fell apart for a while. The low to it's north weaken as did Andrew, hence not affected by the weakened low. Then the high built back in and moved him west. The rest is history. The same scenario may be setting up with Katia
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Quoting MississippiWx:


Good to see ya, Kman.

We're just having a good natured debate. These debates are much easier when the debaters have respect for one another.


Hi there.

It's always tough when a marginal system is either classified or not classified but there it is. The forecasters at the NHC have to make a call one way or another. They are no strangers to these debates even internally, if I had to make a guess Lol
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2545. Delsol
When should we expect HH missions into Katia?
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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.