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 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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When should we expect all of the Heavier rain Pat?
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2143. vince1
Quoting HurricaneNewb:
Oh no Columbian cupid.com is getting me in trouble with the wife tryin to tell her its an advertisement on this blog. Might be time to upgrade my membership. anyone know if the adds go away if you upgrade? Tia

Sounds like you need a wife upgrade to me.
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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?


Forgot where I read it but somewhere said the center could relocate under the deepest convection.
Member Since: August 24, 2010 Posts: 0 Comments: 245
So many storms have had their names stolen this year.. Remember Don? We were calling him pre-Cindy. Remember Harvey? We were calling him pre-Franklin.. then pre-Gert. Remember Katia? We were calling her pre-Jose. Wouldn't be surprised if "pre-Lee" ends up being Maria and 94L steals Lee. XD
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2140. Kibkaos
The GFS model does show the Houston area getting some much much needed rain. Any opinions on this?
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2139. bappit
Quoting Patrap:

Looking at that loop, seems like the convergent flow from the upper low over south La. and the anticyclone over south texas squeezed the air over Houston today. Maybe that made it hotter than expected.
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Me thinks the greek alphabet will be used this season...
Member Since: July 6, 2010 Posts: 113 Comments: 32275
Quoting laguna2:


I totally agree. This is NOT your usual, run-of-the-mill drought...even for Texas. This one + the hottest summer EVER (by a long shot) is almost beyond description for those who haven't endured it. Texas and the contiguous drought areas around it need a drought buster. The most likely candidate (aka SAVIOR) is a tropical cyclone. I've lived through several hurricanes and tropical storms in my 50+ years, and I can honestly say that this drought is as devastating as ANY of them including Beulah and Allen, both major storms. In fact, it may be worse because it's a slow death that rates very little attention and no relief. Whereas, with a tropical cyclone re-building can start after it's over. (And yes, there have, sadly, been plenty of deaths from this drought and heat wave also.)

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.
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Quoting SamWells:


Agreed, but waiting on a few models to update the graphics because some older ones show a westerly drift and the center coming into Northern Mexico. I am beginning to think that was very wishful thinking, too.


It's still possible this come farther southwest, but I doubt it, given that it should be strong enough to feel the pull of the trough once the shear abates.
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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?
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2134. IKE

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so they made it official and gave him a number - 13. Can't they just skip 13 and got to 14? I never think of anything given the number 13 as lucky. Still not looking to great on the west side. But Lawdie the rain...
Member Since: September 5, 2007 Posts: 0 Comments: 3488
2132. IKE

Quoting breald:



IKE!!! Haven't see you in awhile. Nice to see you back.
Yo bud. Nice to c u 2.
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Quoting interstatelover7165:
Wait where and when was Lee? Did I miss it?
Ahhh, all these systems are messing up my head. I said that thinking that 13L would become Lee first, but who knows, 94L might beat him/her to it depending on how the NHC is feeling tonight/in the morning.
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2130. THL3
Quoting want2lrn:


Hey Patrap, can you move that Easter egg over to the west please!


The intersection of 95 & 30 would be nice!!!
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Quoting Patrap:


Westbank will get it too this time seems.


Well I guess I will keep y'all posted but I know Pat will see on the local news. Westbank by the way seems to get messed up a lot lol. Good luck to all in the NO area.
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2128. mig123
Quoting caneswatch:


I'm in South Florida. Personally, I have no immediate concerns, it's just something i'm watching.


me too...i'll keep my eye on her
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2127. KC2NOLA
Quoting Bijou:
The Jefferson neutral ground is an option.

I'm in the neighborhood too, but a couple of blocks closer to the river. Driving home from work I was sort of surprised at the lack of cars on the neutral ground. I've been here 20 years and lived through some nasty rainstorms and never had street flooding. I'm hoping that trend will continue. However, parts of Magazine has been known to entertain some minor flooding:)



Yeah, I thought I would see more as well. Jefferson just leaves me nervous simply b/c of high volume. But- better safe than sorry.
Where I live on Magazine has a tendency to retain water...but that was before all the "new roadwork"! Which was a nightmare, so hopefully the sound of a jackhammer at 6am is worth it now!
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2126. breald
Quoting IKE:




IKE!!! Haven't see you in awhile. Nice to see you back.
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Quoting MiamiHurricanes09:
That's the same T-number Jose had just prior to classification. I wouldn't be surprised if we wake up to Maria, should DMAX help it out a lil' bit.


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.
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2123. IKE

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Quoting MiamiHurricanes09:
That's the same T-number Jose had just prior to classification. I wouldn't be surprised if we wake up to Maria, should DMAX help it out a lil' bit.
Wait where and when was Lee? Did I miss it?
Member Since: August 18, 2011 Posts: 0 Comments: 994
2121. centex
Don't be surprised if we get relocation. Very common early stages of development.
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Quoting stormpetrol:


I think that one is a "possible" caribbean cruiser!

i think so too!!
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Quoting KoritheMan:


If a center reformation occurs with TD13, it won't be along the western end of the gyre, because there is no convection in that area. Not to mention it is still battling shear.


Agreed, but waiting on a few models to update the graphics because some older ones show a westerly drift and the center coming into Northern Mexico. I am beginning to think that was very wishful thinking, too.
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2118. Patrap
Quoting Bijou:
The Jefferson neutral ground is an option.

I'm in the neighborhood too, but a couple of blocks closer to the river. Driving home from work I was sort of surprised at the lack of cars on the neutral ground. I've been here 20 years and lived through some nasty rainstorms and never had street flooding. I'm hoping that trend will continue. However, parts of Magazine has been known to entertain some minor flooding:)



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.
Member Since: July 3, 2005 Posts: 426 Comments: 128667
Quoting extreme236:
TD13 definitely has a lot of work to do, but could be a big storm.

01/2345 UTC 26.4N 91.3W T1.0/1.0 13L -- Atlantic
01/2345 UTC 37.6N 63.7W T1.5/1.5 94L -- Atlantic
That's the same T-number Jose had just prior to classification. I wouldn't be surprised if we wake up to Maria, should DMAX help it out a lil' bit.
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2116. mig123
physic....lol

Quoting NCSCguy:
I seem to remember some physic twins that predicted a hurricane moving up the eastern seaboard sometime this season....
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2115. KC2NOLA
Quoting nola70119:


I can tell you some places in Mid-City that I know won't flood, they didn't after Katrina....but uptown I think you are taking your chances. Elevated parking garage is always good, in the CBD or there is a large lot on North Rampart off the Quarter.


Thanks!
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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


Do not be depressed just yet. I am in midtown Houston and there is still a good possibility this thing moves farther west than the NHC is saying right now. Wait at least until tomorrow around this time to be depressed! We still have a good chance of getting at least 2-4" of rain out of this. We certainly need a lot more and an Allison scenario would probably help us out a lot. Especially going into next year. If we go into next year with -30"+ of annual rainfall the drought next summer will be so much worse. WE need a good 10-15" of rain over the next 3 days or so to at least get moisture into the soil to save our trees (whats left of them) and our foundations!!!
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Quoting MiamiHurricanes09:
Pretty far west on the 00z TVCN.

AL, 12, 2011090200, 03, TVCN, 168, 308N, 733W, 0, 0, , 0, , 0, 0, 0, 0,


Katia looks a little better on the latest images...but probably still a TS.
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Quoting Patrap:


Hey Patrap, can you move that Easter egg over to the west please!
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2111. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 128667
Pretty far west on the 00z TVCN.

AL, 12, 2011090200, 03, TVCN, 168, 308N, 733W, 0, 0, , 0, , 0, 0, 0, 0,
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TD13 definitely has a lot of work to do, but could be a big storm.

01/2345 UTC 26.4N 91.3W T1.0/1.0 13L -- Atlantic
01/2345 UTC 37.6N 63.7W T1.5/1.5 94L -- Atlantic
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2107. Bijou
The Jefferson neutral ground is an option.

I'm in the neighborhood too, but a couple of blocks closer to the river. Driving home from work I was sort of surprised at the lack of cars on the neutral ground. I've been here 20 years and lived through some nasty rainstorms and never had street flooding. I'm hoping that trend will continue. However, parts of Magazine has been known to entertain some minor flooding:)

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.
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2106. Patrap
Dvorak is brightening up and rounding nicely tonight.

Member Since: July 3, 2005 Posts: 426 Comments: 128667
Quoting Patrap:

wunderful,..not




patrap, this puts us on the worst side - what are the rain predictions for the northshore - washington parish - havent seen much on the news.
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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


LOL, we had a "Don" party at a beach Tiki Bar and we could see the thing flailing offshore and failing 10-20 miles offshore.

We got about a dozen streamer showers today by the coast and I think most of the rain fell as verga, evaporated before it hit the ground. Need a real game changer here.
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coc going to reform further south on t.d. 13. what say you pat?
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LOL -- It was beautiful crossing the Mid-Bay Bridge this evening (Destin) you could see the  clouds curved from outer band of storm with just a bit of sun peeking out.  Tomorrow could be another story........  Gonna blow out the Labor Day Weekend.  
Quoting NavarreMark:
Its cloudy outside and the winds out of the SE. I'm scared.

I'm praying that Ike, the Storm Whisperer, comes along and protects me from harm.

Where are ya when I need ya bro?

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2101. Patrap
Quoting nolacane2009:


Unfortunately I am in Terrytown. Big flood zone 1.5 below sealevel. I am very concerned with all the ran. We had 7 inches in a few hours and the water was 3 feet from my house. We shall see.


Westbank will get it too this time seems.
Member Since: July 3, 2005 Posts: 426 Comments: 128667
Quoting Patrap:


No Im 20 ft elevation near Audubon bend by Magazine and Jefferson.

r at a Glance
Weather Station
Uptown, New Orleans
Elevation
20 ft


Unfortunately I am in Terrytown. Big flood zone 1.5 below sealevel. I am very concerned with all the ran. We had 7 inches in a few hours and the water was 3 feet from my house. We shall see.
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Quoting SamWells:


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.


If a center reformation occurs with TD13, it won't be along the western end of the gyre, because there is no convection in that area. Not to mention it is still battling shear.
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TAWX, yep i guess agree, but not for several days, for like 2 weeks or 3,4,5,6,9...lol
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Once that ULL gets out of the picture, things could change in hurry!
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2096. IKE

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just saw the nhc forecast cone. gotta say i completely disagree. i thought it would be a HUGE circle..
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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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