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 FrankZapper:
Katia and Lee are the players now. Lee may not be. He is Lee,a big rainmaker. Now Katia (just like Katrina) could be the one to remember. Katia could be the one. Irene was an appetizer.


Good evening, Kerry.

Lee reminds me a lot of our other notoriously wet systems in the past, like Frances in 1998 and Allison in 2001.
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Quoting TropicalAnalystwx13:


You mean the model that nailed Irene?
I think the northern Islands can be in trouble if this western tendecy continues, not a direct hit, but plenty of rain for sure,... talking about Katia, obviously
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Quoting Dakster:


Why??? Is Charlie Sheen been spotted in the area?


False alarm...


It was just Emilio Estevez...
Member Since: September 22, 2005 Posts: 18 Comments: 2343
Can't wait to see the first DOOMCONE. Prolly a big circle.
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Katia and Lee are the players now. Lee may not be. He is Lee,a big rainmaker. Now Katia (just like Katrina) could be the one to remember. Katia could be the one. Irene was an appetizer.
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Quoting Dakster:


Why??? Is Charlie Sheen been spotted in the area?


nope....Hurlo.:^(
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1688. Vero1
Maria behind Katia?

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1687. Kibkaos
Sitting here in Pearland TX outside in 98 degree heat at 6:00. We need rain now. This is the biggest tease yet. So close but yet so far.
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Quoting weatherb0y:
Is it out of the realm that the low level circulation with 93L (unofficially TD 13) could relocate farther to the southeast around roughly 25N and 88W where that big blowup of convection is?
Levi? :)
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Well latest runs look a lot better for Bermuda so I am kind of happy but then again the East Coast of the US could use a break after they were hit by Irene.
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Quoting P451:
:)




You're so picky.
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Quoting P451:
Decaying surface feature into a large broad area of low pressure with multiple wind shifts? CHECK.

MLC no where near the LLC? CHECK.

Little to no convection over the LLC? CHECK.

Huge area of thunderstorms stretched along a trof? CHECK.

Random wind gust on a buoy to TD strength on the northern reach of the system? CHECK.

Barely measurable west winds for 100s of miles on the south side of the storm? CHECK.

High wind shear? CHECK.

Proximity to NOLA? CLOSE.

TROPICAL DEPRESSION DECLARED.

With this kind of lax criteria needed to declare this system I can't believe it's not TD 16.

Consider the BOC system earlier this year that was left to landfall without declaration.

Earlier today 94L looked as good as Franklin ever did - but was left to go away.

Also a similar entity that looked as good if not better than Franklin in a similar spot as today's 94L? Left to go away.

But I guess they weren't near NOLA and the NHC wasn't being bombarded with calls from angry WU bloggers demanding LEE be declared with 50kt winds on it's first advisory. So they are inconsequential.

:)

See I was telling you earlier they were going to declare, I'm surprise they didn't declare 94L in the process for all the reasons you said earlier.
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Quoting P451:


I think they used all they have on Irene. It was like a carpet bombing.
LOL
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1680. Dennis8
Quoting Levi32:
I see we have TD 13...a bit sooner than I expected, but the NHC this year has been willing to put these systems into forced labor in order to birth them in time to put warnings up sufficiently in advance for nearby land areas.


It is Labor day weekend
Member Since: August 15, 2008 Posts: 0 Comments: 446
Quoting PrivateIdaho:


I told'em to fly clockwise but nooooo.



ROFLMAO!
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Quoting aquak9:

It's ok. The pups will understand, the kids will enjoy having you around. There'll be more dog shows.


I should clarify, my 'kids' are 17, 18 and 27 (oldest, 29, is in Afghanistan) and my daughter-in-law who turns 27 tomorrow. But in my heart they will always be my 'kids'. But you're right, I'm very blessed and my kids and I have great times together. Hurricanes means hours of Rummy 500 together and other games.
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1676. aquak9
LouisianaWoman- review your preps for a tropical storm, be prepared to bug out if needed. Sounds like you know the drill. Fill the meds, fill the gastanks, get enough staples for a few days. Listen to your local emergency managers if it comes to that.
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Quoting AtHomeInTX:
Yes! Bring it on !!!!




Raining a little at my house right now....thank goodness!
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Quoting Dakster:


Why??? Is Charlie Sheen been spotted in the area?
Yes!!.
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1672. Dakster
I hope the UKMET as it relates to Katia is WRONG... That just reminds me of an Andrew type track all over again... Bad, bad, memories...
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1671. emcf30
Quoting hahaguy:
The nogaps really wants to go to disney world.

Not welcome here
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Quoting PrivateIdaho:


I told'em to fly clockwise but nooooo.


Heh, try that in a hurricane. I can see the blog now; "Why/How are they flying backwards?"
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Quoting AtHomeInTX:
Yes! Bring it on !!!!




A little more north of DeRidder, please.
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1668. aquak9
Quoting aislinnpaps:


Yeah, just emailed my friends and told them I'm not going. Another one also is cancelling going. I couldn't deal with worrying about them if I wasn't here. Never really was any doubt I'd cancel, just had to admit it. *S*

It's ok. The pups will understand, the kids will enjoy having you around. There'll be more dog shows.
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Is it out of the realm that the low level circulation with 93L (unofficially TD 13) could relocate farther to the southeast around roughly 25N and 88W where that big blowup of convection is?
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I wonder how many dropsondes will be dumped around Katia once she gets closer and they start flying into her. Guess well have a clearer idea of direction once that starts happening.
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check back in later. Got to feed the kids and get them ready for school tomorrow. Later...
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting Dakster:


Why??? Is Charlie Sheen been spotted in the area?


Winning!
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1663. emcf30
Quoting Tazmanian:
re post


we now have TD 13


BEGIN
NHC_ATCF
invest_RENUMBER_al932011_al132011.ren
FSTDA
R
U
040
010
0000
201109012228
NONE
NOTIFY=ATRP
END
INVEST, AL, L, , , , , 13, 2011, DB, O, 2011083118, 9999999999, , , , , , METWATCH, , AL132011
AL, 13, 2011083100, , BEST, 0, 214N, 845W, 25, 1012, DB, 0, , 0, 0, 0, 0,
AL, 13, 2011083106, , BEST, 0, 225N, 855W, 25, 1012, DB, 0, , 0, 0, 0, 0,
AL, 13, 2011083112, , BEST, 0, 236N, 865W, 30, 1012, DB, 0, , 0, 0, 0, 0,
AL, 13, 2011083118, , BEST, 0, 241N, 870W, 30, 1012, DB, 0, , 0, 0, 0, 0, 1014, 100, 75, 0, 0, L, 0, , 0, 0, INVEST, S,
AL, 13, 2011090100, , BEST, 0, 245N, 875W, 30, 1010, DB, 0, , 0, 0, 0, 0, 1014, 100, 75, 40, 0, L, 0, , 0, 0, INVEST, M,
AL, 13, 2011090106, , BEST, 0, 256N, 887W, 30, 1010, DB, 0, , 0, 0, 0, 0, 1013, 100, 75, 40, 0, L, 0, , 0, 0, INVEST, M,
AL, 13, 2011090112, , BEST, 0, 261N, 900W, 30, 1008, DB, 0, , 0, 0, 0, 0, 1013, 140, 90, 40, 0, L, 0, , 0, 0, INVEST, M,
AL, 13, 2011090118, , BEST, 0, 266N, 914W, 30, 1010, DB, 34, NEQ, 0, 0, 0, 0, 1013, 180, 75, 40, 0, L, 0, , 0, 0, INVEST, M,


Going to be a interesting week.
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Quoting aquak9:


Stay home w/the kids. Go get some ice cream. There'll always be more dog shows. There won't always be more time w/the kids.


Yeah, just emailed my friends and told them I'm not going. Another one also is cancelling going. I couldn't deal with worrying about them if I wasn't here. Never really was any doubt I'd cancel, just had to admit it. *S*
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1661. ackee
BASE on what I am seeing does seem like the threat of KATIA to bermuda HAS decrease while the threat to the us have increase all the models seem be trending more west still early models will shift again but that how its looks now to me
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Quoting will40:



Savannah that site wont let us paste images like they use to. I found that out today when i tried.


Gotcha- guess I need to start uploading... and I'm too lazy for that...
Member Since: September 22, 2005 Posts: 18 Comments: 2343
At what point will we get a better idea on intensity? I mean...obviously if it doesn't end up making landfall this weekend I am sure the chances increase. My biggest issue is when Ike made landfall in Galveston as a Cat 2...he flooded my neighborhood. When Rita made landfall as a cat 3 she wiped out my neighborhood with flooding. So, with either one of these tracks fair game, or even closer (between a Rita and Lily type track) flooding is a very real possibility for me, which increases the longer Lee stays offshore. If it's a tropical storm we can handle that. If it's anything more than that, we've got issues. I need to know if I need to make plans for a major evac--or a tropical storm. UGH! I wish my hubby wasn't stuck on a rig offshore right now.
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1658. will40
Quoting AtHomeInTX:
Yes! Bring it on !!!!





thats cuzz i didnt send the shield back lol
Member Since: September 19, 2005 Posts: 2 Comments: 4266
1657. Dakster
Quoting washingtonian115:
Hide your kids hide your wife!!!!!


Why??? Is Charlie Sheen been spotted in the area?
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1655. ncstorm
Quoting AtHomeInTX:
Yes! Bring it on !!!!




Woohoo!
Member Since: August 19, 2006 Posts: 13 Comments: 16041
Quoting P451:


Recon has flown so many circles around 93L that apparently doomicane13 has formed as a result.


I told'em to fly clockwise but nooooo.
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Yes! Bring it on !!!!


Member Since: August 24, 2010 Posts: 0 Comments: 252
Quoting P451:


Recon has flown so many circles around 93L that apparently doomicane13 has formed as a result.
Hide your kids hide your wife!!!!!
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1651. Levi32
I see we have TD 13...a bit sooner than I expected, but the NHC this year has been willing to put these systems into forced labor in order to birth them in time to put warnings up sufficiently in advance for nearby land areas.
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1648. Dakster
Quoting Clearwater1:
lol
Shields up. You said it before me. But remember, if we are in the cone first, then the storm will def. miss us. . Historically speaking with tongue-in-cheek.


Yes... I like being in the cone 5 days out... It surely will miss us!
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Quoting NICycloneChaser:
Katia is really going to have to be watched, models trending considerably west. Even the GFS, which was on the eastern edge of the guidance, now has Katia fairly close to the Outer Banks. I think she'll be a close call, like Earl.
An Earl track was discussed on the blog yesterday.Ahhhh Early(Earl).Everyone thought he was going to be on his marry way........Until he wanted to screw Labor day weekend up for people.
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1646. DFWjc
Quoting AtHomeInTX:

Not crazy at all. I feel for those people. They thought they were going to get to move back to their homes today. Hope they get a handle on the flames soon.


WISE COUNTY — Firefighters battled a large brush fire in Wise County that reamined uncontrolled Wednesday night. Two homes were lost to the flames.

The fire, centered around the town of Cottondale, started near County Road 3547 just after 1 p.m. and continued to burn nearly three hours later. Dry grass and trees fueled the blaze. At least one person was injured and was taken to a hospital in Bridgeport for treatment. HD Chopper 8 pilot Troy Bush said the fire appeared to double in size between 3 and 4 p.m.

Officials are unsure the size of the fire. At least 200 acres were thought to be burning and about 20 homes were threatened. However, sheriff's department officials said they could not be sure how many homes were in danger because there are many unmarked, dirt roads in the area. A ranch building adjacent to a barn burst into flames as the fire swept through the area. It appeared that propane tanks were ignited by the fire, adding to the inferno.

At least two mobile homes were destroyed by the flames. An estimated 50 to 60 people were evacuated from the area. The original fire command post on County Road 3457 has been abandoned due to advancing flames.

The Tarrant County Task Force and firefighters from five counties have all responded to the fire, with volunteers working on creating fire breaks using bulldozers, water and chemical agents. Texas Forest Service helicopters arrived at the scene and air attack choppers were requested to help control the fire's spread. News 8 was told one firefighter may be injured, but there was no word on that person's condition. Another large range fire continued to burn near Possum Kingdom Lake in Palo Pinto County on Wednesday, fueled by dry conditions, high temperatures and low humidity.
Member Since: July 19, 2011 Posts: 1 Comments: 1006

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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.