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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just saw the nhc forecast cone. gotta say i completely disagree. i thought it would be a HUGE circle..
Member Since: Posts: Comments:
2094. KC2NOLA
Quoting PcolaDan:


Omaha? ;)


Haha, I deserve that. I ask because this city has limited parking as is...let alone "high" parking. I parked my car in Loyola's parking lot before Cindy and got a big fat ticket.

So..I was hoping for a no-ticket type of location ;)
Member Since: Posts: Comments:
Quoting KC2NOLA:
Well Patrap we must be neighbors b/c I live right off Jefferson/Magazine. Do you have a suggestion about a good place to park if the rain is as bad as they forecast?

Ive lived here 9 years, but have never been present for a tropical entity. Thanks.


I can tell you some places in Mid-City that I know won't flood, they didn't after Katrina....but uptown my knowledge is not great. Elevated parking garage is always good, in the CBD or there is a large lot on North Rampart off the Quarter.
Member Since: Posts: Comments:
2092. Patrap
Green in da FunkTop,







..well dats not good

Member Since: July 3, 2005 Posts: 427 Comments: 129418
Quoting mig123:


thats what I was looking at


I'm in South Florida. Personally, I have no immediate concerns, it's just something i'm watching.
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2090. Patrap
Rainbow Image-O-Doom

Member Since: July 3, 2005 Posts: 427 Comments: 129418
Quoting HurricaneDean07:
TAWX, How long has it been since you left TX? The Drought hasnt been this bad in at least 2 to 5 decades, and a matter of fact If a La Nina returns then we need the rain now, or else all its going to do is get worse... Just need RAIN, and am Anxious to get it, tired of seeing Burnt spots every 10 yards on the highway, and Dead grass the common thing around here. Im tired, Just TIRED of this, and after the "Don" incident i just want to see some drops on my windshield, or wet concrete, or at least some drops from the drainage... :(
Im depressed now


Left in March...I wish Texas had rain too, but not heavy rain, not for a long time, like what would occur. Light to steady rain for several days... :)

Member Since: July 6, 2010 Posts: 113 Comments: 32690
Quoting KoritheMan:


Or use Adblock. ;)
Thx beach and Kor will do that.
Member Since: Posts: Comments:
2087. Patrap
Quoting atmoaggie:
Ah, my birthplace (and 2 generations of ancestors). I remember like it was yesterday...

;-)


Me too...and Jr. as well.
Member Since: July 3, 2005 Posts: 427 Comments: 129418
2086. DFWjc
Quoting HurricaneDean07:
TAWX, How long has it been since you left TX? The Drought hasnt been this bad in at least 2 to 5 decades, and a matter of fact If a La Nina returns then we need the rain now, or else all its going to do is get worse... Just need RAIN, and am Anxious to get it, tired of seeing Burnt spots every 10 yards on the highway, and Dead grass the common thing around here. Im tired, Just TIRED of this, and after the "Don" incident i just want to see some drops on my windshield, or wet concrete, or at least some drops from the drainage... :(
Im depressed now


AMEN TO THAT!!
Member Since: July 19, 2011 Posts: 1 Comments: 1006
Quoting lottotexas:
He's on Barometer Bob

Link

Good god is barometer Bob on ludes?
Member Since: Posts: Comments:
2084. Patrap
Member Since: July 3, 2005 Posts: 427 Comments: 129418
Quoting Patrap:


Baptist Hospital, or other parking high space
Ah, my birthplace (and 2 generations of ancestors). I remember like it was yesterday...

;-)
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting atmosweather:


Hurricane Humberto in 2008...from TD to Category 1 in 18 hours.


Yeah I called that storm when it was just some showers that converged off South Padre island in lower Texas. By the time it floated up to Corpus Christi offshore, it was a raging thunderstorm that was beginning to rotate. No big storm, Humberto did make it to Cat-1 shortly thereafter, and before coming ashore near High Island near Beaumont.

TD 13 seems totally different in nature to me, just a downcast kind of opinion right now. But could there be some surprises? Could things relocate to the west? Hmm, I guess we'll see what the overnight crew says.
Member Since: Posts: Comments:
TAWX, How long has it been since you left TX? The Drought hasnt been this bad in at least 2 to 5 decades, and a matter of fact If a La Nina returns then we need the rain now, or else all its going to do is get worse... Just need RAIN, and am Anxious to get it, tired of seeing Burnt spots every 10 yards on the highway, and Dead grass the common thing around here. Im tired, Just TIRED of this, and after the "Don" incident i just want to see some drops on my windshield, or wet concrete, or at least some drops from the drainage... :(
Im depressed now
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Quoting Beachfoxx:
Buy a membership - NO ads.



Or use Adblock. ;)
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Quoting Patrap:
dry air doesn't want to leave Texas
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Katia is starting to look like a big red blob now on the rainbow loop, i think she is wanting to compete with pre Lee as to who can create the bigger blob.
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not a wind event

but...



lot of rain about to be over my house
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2075. Patrap
Member Since: July 3, 2005 Posts: 427 Comments: 129418
IMO... TD13 is still in it's developing phase, NHC forecast cone or Baloon in this case will likely shift several times. Too hard to predict stalled systems so TX should not get their hopes for rain down...IMO
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Quoting ackee:
I THINK THAT WILL BE OUR NEXT NAME SYSTEM


I think that one is a "possible" caribbean cruiser!
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2072. bappit
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 ;)

The 19-20 inch bomb is a bit speculative though, as Allison demonstrated, certainly possible.

Where I am at ... I'd take it. Other people sure would not. Of course, it doesn't look like it is coming here anyway.
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2071. mig123
Quoting caneswatch:


There will be, however, a high coming into the Atlantic from the midwest. That alone bears watching Katia.


thats what I was looking at
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Buy a membership - NO ads.
Quoting HurricaneNewb:
Just ran all my scans earlier today clean system, i beleive it might be region or ip related adds for specific areas, like facebook does, but if upgrading memebership makes all adds go away i will do that.

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2069. Patrap

wunderful,..not


Member Since: July 3, 2005 Posts: 427 Comments: 129418
Quoting KC2NOLA:
Well Patrap we must be neighbors b/c I live right off Jefferson/Magazine. Do you have a suggestion about a good place to park if the rain is as bad as they forecast?

Ive lived here 9 years, but have never been present for a tropical entity. Thanks.


Omaha? ;)
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Been lurking here for years during hurricane seasons and just thought I'd finally sign up, pop in and say "hello"!
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Quoting aislinnpaps:


TA13, when you are watching your cattle and horses die and your crops are dead and there are bills to pay... Even if it floods, it'll help. If no rain, this drought could continue until next March even. More deaths, more people losing their homes and way of living. Not to mention the fires that are increasing and getting harder and harder to put out.


Texas can't win either way :(
Member Since: July 6, 2010 Posts: 113 Comments: 32690
2065. Patrap
Member Since: July 3, 2005 Posts: 427 Comments: 129418
Quoting lottotexas:
He's on Barometer Bob

Link


Thanks :)
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2063. Patrap
Member Since: July 3, 2005 Posts: 427 Comments: 129418
2062. Patrap
Member Since: July 3, 2005 Posts: 427 Comments: 129418
Quoting bappit:

Bermuda is land the last time I checked.


A 40mph storm, not warm core, that formed 60 wiles west of Bermuda and moved due North is not that much of a threat. My point was that it seems the TPC is in a hurry sometimes to name something just for the sake of issuing a name.
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Really Weird this TD #13 !!!!!
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2059. ackee
Quoting thedawnawakening3:
The tropical wave behind Katia is in a very dangerous position, around 30w and 8-9n.
I THINK THAT WILL BE OUR NEXT NAME SYSTEM
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Quoting CaneHunter031472:
Levi!! Where are you??
He's on Barometer Bob

Link
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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 ;)


TA13, when you are watching your cattle and horses die and your crops are dead and there are bills to pay... Even if it floods, it'll help. If no rain, this drought could continue until next March even. More deaths, more people losing their homes and way of living. Not to mention the fires that are increasing and getting harder and harder to put out.
Member Since: Posts: Comments:
2056. Patrap
Quoting KC2NOLA:
Well Patrap we must be neighbors b/c I live right off Jefferson/Magazine. Do you have a suggestion about a good place to park if the rain is as bad as they forecast?

Ive lived here 9 years, but have never been present for a tropical entity. Thanks.


Baptist Hospital, or other parking high space
Member Since: July 3, 2005 Posts: 427 Comments: 129418
2 Big questions.........

1. will Katia noodles trend more to the west?

2. will 93l move more to the east??
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Quoting atmoaggie:
Yeah, ours are snap-crash.

The uprooting ones are *usually* seen leaning on a house, rather than laying completely through it.

An Irene example (and not even a very good one):


Another:


Saw a great many around here post-K where the tree trunk literally cut the house in two and the trunk was laying on the foundation.

Yep everywhere around here after Rita.  That's what happened to my mobile home. Yeah, I know all the jokes. Lol. 90 ft oak went smack down the middle. Didn't break one window but blew the walls out broke the steel frame under the house, went to the ground. Looked like a giant hotdog with a lot of relish on it. Lol. Ah memories. :)
Member Since: August 24, 2010 Posts: 0 Comments: 253
GFDL Predicts a weak Cat 1. I think that now that there is more data to feed the GFDL we should get a more accurate forecast for the next run, but officially speaking the latest 12z run stated that.
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Quoting HurricaneDean07:
TAWX,
The last thing Texas needs right now is 93L/TD #12/Lee, or whatever you want to call it. 93L promises to be a HUGE rain-maker, and torrential rains up to 20" is not good for Texas. It would cause significant flooding, and would probably be as damaging as Tropical Storm Allison (2001).

What Texas needs is several days of LIGHT rain, nothing heavy.

Sorry, but that is completely the opposite of what we need.
Any kind of rain, we dont CARE, AT ALL. let it be an allison, let it flood, we need 18 inches of rain out of the 20 anyway. Dont be calling out to TX and telling us what we dont and should need, RAIN is RAIN, and we need ALOT OF IT NOW.
Don't Mess With Texas, boy...


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 ;)
Member Since: July 6, 2010 Posts: 113 Comments: 32690
Quoting Patrap:
Vermont showed during Irene and many other areas..being above or below sea level means diddly under the right situ.
+1 although it's never good to be below sea level unless I'm missing something. This is sort of like being chased by a bear, you don't have to be the fastest runner, just not the slowest. In other words have someplace near you that's enough lower for the water to run to there.
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2050. emcf30
Quoting Patrap:



Down from Spring as we have been below normal in Rainfall.


Good to hear. If the HPC forecast pans out, you all will need every bit of space to hold the water that is projected.
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Alright I doubt i have school tomorrow, im north of new orleeans, pressure has just droppe from 1015 milibars to1012 milibars in 3 or 4 hours this could be a long week ill keep yall upated
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2048. KC2NOLA
Well Patrap we must be neighbors b/c I live right off Jefferson/Magazine. Do you have a suggestion about a good place to park if the rain is as bad as they forecast?

Ive lived here 9 years, but have never been present for a tropical entity. Thanks.
Member Since: Posts: Comments:
Quoting atmoaggie:
Humberto was 2007.


Lol you're right...my brain is soooo fried.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
TAWX,
The last thing Texas needs right now is 93L/TD #12/Lee, or whatever you want to call it. 93L promises to be a HUGE rain-maker, and torrential rains up to 20" is not good for Texas. It would cause significant flooding, and would probably be as damaging as Tropical Storm Allison (2001).

What Texas needs is several days of LIGHT rain, nothing heavy.

Sorry, but that is completely the opposite of what we need.
Any kind of rain, we dont CARE, AT ALL. let it be an allison, let it flood, we need 18 inches of rain out of the 20 anyway. Dont be calling out to TX and telling us what we dont and should need, RAIN is RAIN, and we need ALOT OF IT NOW.
Don't Mess With Texas, boy...
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Quoting mojofearless:


I don't think I've ever seen that ad, actually. Sure you don't have some sort of malware?
Just ran all my scans earlier today clean system, i beleive it might be region or ip related adds for specific areas, like facebook does, but if upgrading memebership makes all adds go away i will do that.
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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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