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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2495. Dennis8
Quoting TropicalAnalystwx13:


(nods)
Quoting TropicalAnalystwx13:


A tropical depression by tomorrow? We have one now ;)


Su
Quoting Joshfsu123:
NHC makes the decision - they know what they are doing. Deal with it.


Thank you...
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2494. KEEPEROFTHEGATE (Mod)
T.C.F.W.
012/H/K/C1
MARK
16.95N/50.95W


Member Since: July 15, 2006 Posts: 174 Comments: 54449
I think some on here just want to complain about something

and when there is nothing to complain about they make up something to complain about


I don't agree 100% that this should be classified either, but I can understand why. A key point in this is that steering is weak and because of that, we truly do not know how long this will be over water. Plus with winds to TS force already in parts of the system, TS type conditions could be impacting the coastline as early as tomorrow.
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Okay so the issue is there so much convection, they could issue flood warninggs alone but its so close to cyclone status that they might as well declareit so thats my two cents take it or leave it
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I'm thinking it's pretty close to becoming a hurricane again...probably at 5a.m.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
2489. DFWjc
Quoting nolacane2009:


Well that might be the case in the city but in my case on the westbank in Jefferson Parish it is 1 inch first hour and 1/2 inch every hour after that. We had 7 inches in a few hours and water was 3 feet from my house.


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....
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2488. yoboi
thanks for the info guys so NOLA could be in for major flooding......will they evacuate after 10 inches of rain????? they seem to worry more about cat size of a storm but looks like they should consider potenial rainfall also...just wow
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Quoting GTcooliebai:
At this rate we might surpass the 2005 Atlantic Hurricane Season, if the NHC keeps wasting names on these pep squeak storms, in fact it will make 2005 seem like a pushover, when in reality it is not! And tarnish the infamous legacy of that year, by putting this year on top as the most active. Hopefully I'm wrong and we don't surpass 2005 as that year should remain in a class of its own.

Did you know:

--Only two storms this year have failed to accumulate at least 1 whole ACE unit (Jose and Franklin). 2005 had six such storms.

--Hurricane Irene was more powerful from an ACE perspective than 25 of 2005's 28 storms (including Katrina).

--Katia has already accumulated more ACE than 12 of 2005's storms.

--Even this year's lightweight Gert managed to gather more ACE than nine of 2005's storms.

My point being that, while 2005 was a spectacular oddity, to be sure, it wasn't as if every storm that year was a long-lived monster; 2005 had its share of "pip squeaks". It had twelve TSs, an unnamed subtropical storm, and an additional three TDs that never became TSs. (And, for the record, seven Cat 1s.)
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Quoting Skyepony:


It is what it is...

2011SEP02 014500 2.0 1009.0/ +0.0 / 30.0 1.9 1.9 1.0 0.1T/hour ON OFF 19.94 2.61 SHEAR N/A 26.90 91.71 FCST

Quoting the ADT handbook page 30 (which I hope you all have read..from cover to cover..)

SHEAR Displaced convection and exposed circulation center


Thank you.
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Quoting P451:


They do know what they are doing.
They do make the decisions.
We will live with it.

However

They clearly threw out the rulebook on this one. To satisfy what or whom I do not know.

We're not talking borderline here. We're talking stretching or ignoring their own checklist to fit the upgrade.

Therefore many of us are uncomfortable with their decision to prematurely upgrade a system that is far from worthy of it.




and I'll ask again

if it is the conservative action, what is the harm? why would it cause you to be "uncomfortable"?
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Quoting kmanislander:
Katia 4 hours ago



Thanks for that kman... If you had just tuned in to tonight's discussion... one would have forgotten Katia is out there.

In light of tonight's debate though, it's worth pointing out that Katia is indeed a bona fide tropical storm.

Don't think that's much of a stretch.
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Most Recent Positions Regardless of Basin:

DATE/TIME LAT LON CLASSIFICATION STORM
01/2345 UTC 26.4N 91.3W T1.0/1.0 13L -- Atlantic

CI MWS MWS MSLP MSLP Saffir-Simpson
Number (Knots) (MPH) (Atlantic) (NW Pacific) Category
1 25 KTS 29 MPH (Approximate)
1.5 25 KTS 29 MPH

It is not a TD by wind speed however it is so close to the coast that warnings of some kind needed to be posted. The NHC made their decision and I think it is good to post the warnings.

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Quoting P451:



With several more days over water there should be no urgency to upgrade the system to a level it is not.

The winds are well removed from the center.
The convection is well removed from the center.
The center is weak and ill defined and broad.
The convection is focused along a trof - it's not a single separate entity.

I have little doubt that tomorrow it will become organized enough to be a tropical depression. I have stated for a couple of days I thought by the third day, which will be tomorrow, we would begin to see significant organization of the system.

My opinion is that right now not only is it not a depression it is not even close.

The purpose of an official agency is to follow a set of guidelines and rules and not bend them based off of hunches.

Our job on this blog is to have opinions and hunches. They as an official agency are supposed to follow strict guidelines regarding the upgrading of systems.

It seems they have forgotten that.

Sign of the times my brotha, stress & the state of the economy don't mix, but hey those guys are the expert and I can stand here and say they flew into the storm today, not us! So they saw something that were not seeing.
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2477. Skyepony (Mod)
Quoting MississippiWx:
TD13, since it's a tropical cyclone according to the NHC, has the look of a sheared tropical cyclone on satellite imagery. It's not a joke. It's not making up the rules as they go. It is what it is.


It is what it is...

2011SEP02 014500 2.0 1009.0/ +0.0 / 30.0 1.9 1.9 1.0 0.1T/hour ON OFF 19.94 2.61 SHEAR N/A 26.90 91.71 FCST

Quoting the ADT handbook page 30 (which I hope you all have read..from cover to cover..)

SHEAR Displaced convection and exposed circulation center
Member Since: Posts: Comments:
Quoting FLdewey:
Cantore has his smart glasses on... can't be good.

The Orleans Parish Sewerage & Water Board's director said there are back up generators at its power plant to try and ensure pumping operations don't go offline during a critical time.
"The pumping capacity is at 100 percent. We will close gates as necessary, but most importantly, it's important that citizens clean their catch basins, clean their drains," said Marcia St. Martin, executive director of the S&WB.


Good idea living in a bowl... DIY Public Works. :-o


Well, as Irene just unfortunately proved, "the bowl" is not the only areas that flood.
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Quoting TropicalAnalystwx13:
13L IS A TROPICAL DEPRESSION...DEAL WITH IT.

#gettingfrustrated


Agreed. Guess they are not in LA or MS
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Katia 4 hours ago

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I understand your reservations P451--but truth be told--no choppers will fly in weather remotely close to what the LA coast is about to experience in the next couple of days. Each chopper can only carry a couple of crew members. With this thing as close as it is and the possibility of loss of life--I can see why the call came early.
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13L IS A TROPICAL DEPRESSION...DEAL WITH IT.

#gettingfrustrated
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Quoting P451:



With several more days over water there should be no urgency to upgrade the system to a level it is not.

The winds are well removed from the center.
The convection is well removed from the center.
The center is weak and ill defined and broad.
The convection is focused along a trof - it's not a single separate entity.

I have little doubt that tomorrow it will become organized enough to be a tropical depression. I have stated for a couple of days I thought by the third day, which will be tomorrow, we would begin to see significant organization of the system.

My opinion is that right now not only is it not a depression it is not even close.

The purpose of an official agency is to follow a set of guidelines and rules and not bend them based off of hunches.

Our job on this blog is to have opinions and hunches. They as an official agency are supposed to follow strict guidelines regarding the upgrading of systems.

It seems they have forgotten that.



How is the center not well-defined? It seemed pretty well-defined from aircraft data. You need to show me where convection is along a trough? Where did the surface wind analysis from the HH show that we have a trough of low pressure, rather than a closed low?
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Quoting DFWjc:


oh and the NWS can't be ever wrong? HA!


please show us a more accurate alternative
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2467. Bijou
S'OK that's good info.

In theory, reality and theory should be the same. In reality, they are not:)

Quoting DFWjc:


just going by what the army corp of engineers have said about the "new" temporary pumps..
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Quoting Jasonsapology:

AND THATS MY OPINION, SO WHATS THE PROBLEM???????

First, all caps represents yelling, which is not needed here.
Second, there is a difference between an opinion and name calling/labeling. People can state when they don't agree, but do it civily. There is no need to call anyone an idiot because you do not agree with them. Disagree, state your reasoning and back it up with some sort of evidence. Don't just call others names because you only want to believe the "experts."
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2464. Skyepony (Mod)
Quoting atmosweather:


You couldn't be more right.


I agree too. Our scale isn't perfect, all that rain is damaging.

TRMM caught the drier side today, but where it is raining it's pouring. Which is how it has been here. Click pic for quicktime animation.
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Quoting P451:


But...if it's not a TD, then, it's not a TD. Issue a flood warning.

So now a system with a 1.0 rating has weakened?

Come'on....... there was no reason to toss the checklist just because the system is near land.

We've seen recon find a closed low in systems plenty of times and we watch the NHC keep them as an invest because of ---- exactly what we see right now: A very disorganized system.

I have little doubt that 93L would eventually become TD13 but I see no reason to upgrade it when it's clearly not.

But, again, my reservations are meaningless given they decided to name it.

However, making the rules as you go is not something an official agency should be doing.
While it was a closed low, it had very weak westerly winds, and thus should have waited for those winds to get stronger and a tighter circulation...judging by the satellite tonight of where they have the center doesn't look impressive atall. Now if the center reforms where the highest connection is, then that should have given them the reason to let this system find its identity, which clearly it does not have one now...Sorry if I sound rude & critical, just stating what I see.
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Quoting twincomanche:
Just tell yourself every day"I refuse to be a victim." This too will pass.
Thanks I try so hard every day but seeing everything dead just bothers me, Thank you to all those out there praying for rain for Texas, it is just a hopeless feeling, we take rain for granted but when it stops for so long you wonder if it will ever rain again.
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Quoting hurricanehunter27:
Why? just cause it does not look pretty does not mean it should not be a TD.


Yeah...fat girls need love too!
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TD13, since it's a tropical cyclone according to the NHC, has the look of a sheared tropical cyclone on satellite imagery. It's not a joke. It's not making up the rules as they go. It is what it is.
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I'm gonna run to the gas station real quick, but I'll leave you guys with a blog update I did on the tropics. Check it out.

Back later.
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Quoting DFWjc:


just going by what the army corp of engineers have said about the "new" temporary pumps..


LOL, I hear you my friend.
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Quoting DFWjc:


just going by what the army corp of engineers have said about the "new" temporary pumps..


Well that might be the case in the city but in my case on the westbank in Jefferson Parish it is 1 inch first hour and 1/2 inch every hour after that. We had 7 inches in a few hours and water was 3 feet from my house.
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Quoting cchsweatherman:
The NHC classifying Invest 93L as TD 13 is an absolute joke.
Why? just cause it does not look pretty does not mean it should not be a TD.
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2452. DFWjc
Quoting Jasonsapology:


The National Weather Service (NWS) provides weather, hydrologic, and climate forecasts and warnings for the United States, its territories, adjacent waters and ocean areas, for the protection of life and property and the enhancement of the national economy. NWS data and products form a national information database and infrastructure which can be used by other governmental agencies, the private sector, the public, and the global community."


oh and the NWS can't be ever wrong? HA!
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Quoting DFWjc:


here's a story about the levee and the temp pumps

Link


Awesome tidbit: The author of that article is the voice of 21 characters in The Simpsons.

Shearer is the man!
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The National Hurricane Center makes the decisions...They declared it a TD, so it is a TD. If you don't like it, write them an email, not like it matters.

Stop bashing the NHC, which most of you were getting mad about with Irene because other people were bashing them. But what are you doing right now?

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2448. LBAR
Quoting GTcooliebai:
At this rate we might surpass the 2005 Atlantic Hurricane Season, if the NHC keeps wasting names on these pep squeak storms, in fact it will make 2005 seem like a pushover, when in reality it is not! And tarnish the infamous legacy of that year, by putting this year on top as the most active. Hopefully I'm wrong and we don't surpass 2005 as that year should remain in a class of its own.


Because the goal is to up the number of storms to correlate with the premise of "climate change" and all of its speculated DOOM. There can be no other explanation. If there is, I want to know it.
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Quoting cchsweatherman:
The NHC classifying Invest 93L as TD 13 is an absolute joke.


yeah, they have no clue(please note sarcasm)
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Quoting Skyepony:


Tropical Depressions are not attached to fronts..it has to cut off first...
I don't think it is attached to a frontal boundary. I'm pretty sure the NHC wouldn't be saying "ONLY A SLIGHT INCREASE IN ORGANIZATION COULD RESULT IN THE FORMATION OF A TROPICAL STORM" if that were the case.

We should have 14L if 13L was classified. I see that's the whole argument this evening, lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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.