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 Drakoen:
I think the NHC jumped the gun in calling 93L a tropical depression, although the uncertainty in the track and intensity may have warranted them renumbering 93L to a tropical depression.


Certainly not consistent with the standards they have applied to previous systems. They are doing an in-house experiment this year which could lead to issuing watches/warnings before formation in the future. Of course that will leave another area for criticism.
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Checking in from Slidell. Alone with no nearby support but I got a truck and a credit card. Thinking about getting out of here early tomorrow A.M. We can't handle this much rain. I work management 70 hours a week in the pipeline business and must report to work tomorrow morning. Advice is welcomed.

Was active on here last year, very nice to see some familiar names here. Stay safe ladies and gentlemen.
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Quoting iahishome:
Hmmm, either this thing is being sheared or the center is not where the NHC says it is...

I'll be watching for relocations to the south in subsequent updates... The more that happens, the worse it is for everyone along whichever strand of spaghetti this thing chooses to follow.


I think there is a combination of the two. As conditions start to improve for development (if they do as forecasted) I dare to say that the COC will be relocated to the SE of where it is right now, but I am hoping this is not the case. As Levi said in the Barometer Show, If Lee is still over water by Monday chances are it will be a Hurricane.
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Both, Luis and Marilyn (1995)were major hurricanes with pronounced, sharp NW turns which affected the east caribbean islands.
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2191. Patrap
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Quoting hurricanejunky:
I know the NHC has it located somewhere else but to me there looks to be a well defined circulation at around 88-89W 24-25N. Anyone else seeing that?



Looks to me over LA at 31N and 92W

But it certainly could move under the heaviest convection..
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2170. I absolutely hate futurecasting like this, but if we're going to see 22 named, I think this is one way it might look like with the rest of the named storms.

Hurricane Maria (September)
Hurricane Nate (September)
Tropical Storm Ophelia (September)
Hurricane Rina (September)
Hurricane Sean (October)
Hurricane Tammy (October)
Hurricane Whitney (October)
Tropical Storm Alpha (November)
Tropical Storm Beta (November/December)
Member Since: July 8, 2005 Posts: 259 Comments: 24471
Quoting stormpetrol:

$64,000 ? I really don't know to be honest. I think the jury is still out on Katia
I agree just looking for another really smart person to agree with me.
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2187. Patrap
New Orleans
NEXRAD Radar

Type
Velocity Azimuth Display Wind Profile ° Elevation
Range
124 NMI

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2186. Levi32
Based on the floater, it's possible that TD 13 may have at least temporarily ceased northward progress, possibly due to some attraction to the convection to the southeast. Reformations of the center could occur within the very broad circulation, but a jump all the way to the convection won't happen at this point. Tomorrow the convection will likely start spreading more over the center, turning our system into a bonafide tropical cyclone.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
Quoting TropicalAnalystwx13:


As of a matter of fact, I lived in Texas for several years, so I know how it would go...

Texas does not need that much rain, sorry to tell ya ;)

That may be right for crops, etc but not the ground water problems. Run off will fill back in some of the city water supplies & wells etc. Give the livestock something to drink! It might not soak the ground as it should but even run off would be a godsend for many places. People are moving off their land because thier wells are dry. Anything is better than nothing.
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2184. HCW
Quoting muddertracker:


Let's go XTRAP!! Verify, baby...Texas is counting on ya..lol!


Xtrap is never wrong :)
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More hype and media is on the bandwagon
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Both, Luis and Marilyn were major hurricanes with pronounced, sharp NW turns which affected some east caribbean islands
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Quoting twincomanche:
So CONUS looks safe?

$64,000 ? I really don't know to be honest. I think the jury is still out on Katia
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looks like the coc isnt where they currently have it.......... if the coc changes to the deepest part of convection we may see the hurricane here in southeat LA
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2179. Drakoen
I mean... LOL

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Shear supposed to fall off tonight and into tomm
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2177. Patrap
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look whats off africa.. thats maria alright.
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Quoting Drakoen:
I think the NHC jumped the gun in calling 93L a tropical depression, although the uncertainty in the track and intensity may have warranted them renumbering 93L to a tropical depression.


Sometimes you do things to make sure people are paying attention.
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Quoting Drakoen:
I think the NHC jumped the gun in calling 93L a tropical depression, although the uncertainty in the track and intensity may have warranted them renumbering 93L to a tropical depression.
cant really blame them though its so close to land
Member Since: July 10, 2006 Posts: 1 Comments: 833
Quoting HCW:


Let's go XTRAP!! Verify, baby...Texas is counting on ya..lol!
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2172. Patrap
Quoting nolacane2009:
When should we expect all of the Heavier rain Pat?


Anytime tonight thru whenever seems.



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Quoting Drakoen:
I think the NHC jumped the gun in calling 93L a tropical depression, although the uncertainty in the track and intensity may have warranted them renumbering 93L to a tropical depression.


Agreed. I don't think the situation was urgent enough where they couldn't wait until the organization improved.
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Think Greek alphabet as well, Forecast for Remaining half of the season...
Lee: Category 1: 80 Mph; September
Maria: Tropical Storm: 50 Mph
Nate: Category 4: 140 Mph
Opheilia: Category 3: 115 Mph
Phillipe: Tropical Storm: 65 Mph
Rina: Category 2: 105 Mph
Sean: Category 4: 150 Mph
Tammy: Category 1: 90 Mph; October
Vince: Tropical Storm: 70 Mph
Whitney: Category 2: 110 Mph
Alpha: Tropical Storm: 50 Mph
Beta: Category 3: 115 Mph; November
Gamma: Tropical Storm: 60 Mph
Epsilon: Category 1: 75 Mph

Season Aftermath:
25 NS
11 Hurricanes
5-6(Depending on if Katia becomes Major)
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Hmmm, either this thing is being sheared or the center is not where the NHC says it is...

I'll be watching for relocations to the south in subsequent updates... The more that happens, the worse it is for everyone along whichever strand of spaghetti this thing chooses to follow.
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Quoting stormpetrol:
Katia looks to be trucking WNW now.
So CONUS looks safe?
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If we (NOLA) get that much rain we are screwed big time...remember 1978 and 1995? 15" to 25" in one and two days repectively in non-tropical evenets no less...the city and surrounding areas were paralyzed. All depends on where this baby sets up with the moisture train guys.
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2166. GetReal
<
Member Since: July 4, 2005 Posts: 204 Comments: 8898
Quoting thedawnawakening3:
The tropical wave behind Katia is in a very dangerous position, around 30w and 8-9n.


The 3pm SJU NWS discusion, which can be found on my blog, says that the next system after katia and any system from africa in the next 7 to 14 days will be a major threat for the antilles and caribbean its actually a good little read.
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2164. Drakoen
I think the NHC jumped the gun in calling 93L a tropical depression, although the uncertainty in the track and intensity may have warranted them renumbering 93L to a tropical depression.
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Katia looks to be trucking WNW now.
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Quoting GTcooliebai:
Yep, I'm thinking somewhere in the middle of that convection around 25 N, 87, 88 W.


From the Horse's mouth, and I quote;

"SINCE THE DEPRESSION IS IN ITS FORMATIVE STAGE THE INITIAL MOTION
IS HIGHLY UNCERTAIN. IN FACT...THE CENTER COULD REFORM WITHIN THE
LARGE CIRCULATION DURING THE NEXT 12-24 HOURS. THE DEPRESSION IS
CURRENTLY LOCATED TO THE SOUTH OF A MID/UPPER LEVEL RIDGE OVER THE
CENTRAL UNITED STATES. THE RIDGE IS FORECAST TO SLIDE EASTWARD AND
WEAKEN DURING THE NEXT 2-3 DAYS...LEAVING THE CYCLONE IN WEAK
STEERING FLOW. THE OFFICIAL FORECAST SHOWS A SLOW NORTHWESTWARD
MOTION DURING THE NEXT 24 HOURS...FOLLOWED BY A TURN TOWARD THE
NORTH AND NORTHEAST. THE NHC TRACK IS IN BEST AGREEMENT WITH THE
GFS AND ECMWF MODELS".
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That deep of convection would have something to do with a jump on coc.



(blue, right-center)
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Nice to meet all the NOLA people on here tonight.. I am in 70119 also.. my street only flooded about 2 1/2 feet for Katrina (Esplanade ridge) and my driveway is a couple of feet above the street so I think I should be ok with my cars at home..
Don't think there is anything stopping you from parking on the roof of the old Schwegmans on Broad and Beinville.
Now.. I will have to be at work thru most of the bad weather and where work is is one of the lowest spots in the city (Jeff Davis and Euphrosine).. wonder if I can get my car into the elevator and up to the second floor :-)

(Yes.. I will be keeping BOB on the air throughout the storm :-) )




Quoting Patrap:


Indeed, esp above Prytania past Claiborne.

We have the Winn Dixie Parking Lot on Tchop for high parking. If it get there, well..itsa gonna be really bad.
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Good nights, Bloggers , your dreams be with the tropics action...
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2158. HCW
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Quoting centex:
Don't be surprised if we get relocation. Very common early stages of development.
Yep, I'm thinking somewhere in the middle of that convection around 25 N, 87, 88 W.
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After all, there is a high atmospheric stability... in the entire atlantic basin. In other words, nothing ocurring is yet as extraordinary as predicted.
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Quoting MiamiHurricanes09:
Indeed. We're at 37 right now (roughly), which is below normal (70 being the threshold for the median)...and pretty much an anomaly when it comes down to having 11 cyclones. Just the result of pee-wee tropical storms that last a few hours lol.


Katia will definitely help boost the ACE...right now she has only contributed roughly 3, but if she attains major hurricane status she will probably produce up to 25-30 or so.
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Experimental HWRF, 12 UTC:


(click for full size)


3km moving nest, from: http://storm.aoml.noaa.gov/hwrfxprojects/?project Name=HFIP Demo 2010
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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

per doc masters, I would say he was about 24 hours late
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2152. vince1
Quoting mojofearless:


I don't think I've ever seen that ad, actually. Sure you don't have some sort of malware?

Or this. Maybe your wife is just mindful of a pattern of behavior. ;)
Member Since: August 6, 2006 Posts: 0 Comments: 210
Quoting totalamature:

I cant agree enough! Its amazing that some people dont feel the TX drought concerns them! Do you eat meat? We are looking at the lowest numbers of breeding cattle & other livestock being kept back in decades. Do you eat Veggies? They'll be at all time highs. The crops are shot. Anything with grain, corn etc shooting thru the roof, From bread to breakfast food & even Dog food. 400 ft wells going dry, city water supplies at all time lows. Animal dying from lack of water. We hear "well cant you just truck water in? From where? The cities were letting People pay & fill water trucks but now most are cuting that off. No winter hay for cattle or horses. If you eat, drive or much else, this drought is going to affect you. Yes, we keep hollering for rain. You should sure hope we get it, instead of being tired of hearing about it.
There is a problem here. Texas votes Republican so therefore they are not to be reported in a sympathetic manner. No matter that it will effect the food chain down the road.
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It is good to see you... looks like we are going to be east of storm. : )
Quoting IKE:

Yo bud. Nice to c u 2.

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2148. palmpt
Quoting sarahjola:
coc going to reform further south on t.d. 13. what say you pat?


Sure looks like that.
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Quoting lottotexas:
He's on Barometer Bob

Link


Great show Levi!
Member Since: October 5, 2010 Posts: 0 Comments: 269
Models depicts "monstruous" systems, but nature comfronts them with the reality-NOT monsters.
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Quoting extreme236:


Yeah I could see that happening...even though we've seen a lot of storms, its gonna take a lot of powerful storms to bring up the ACE.
Indeed. We're at 37 right now (roughly), which is below normal (70 being the threshold for the median)...and pretty much an anomaly when it comes down to having 11 cyclones. Just the result of pee-wee tropical storms that last a few hours lol.
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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.