Gulf of Mexico disturbance 93L a Lousiana flood threat; Katia a hurricane

By: Dr. Jeff Masters , 3:28 PM GMT on September 01, 2011

Share this Blog
26
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 2245 - 2195

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64Blog Index

Quoting twincomanche:
I think tomorrow mid day would be the earliest that I would even be thinking about making a decision. This thing has little direction or strength information to know much yet.


Thank you. I am concerned because this isn't a July or even August storm. Gulf is at 88 degrees and the potential center of circulation is uncomfortably far out with weak steering winds and strong high pressure from the west. I am all too reminded of Allison's effects on Houston. The last thing we need here is a meandering 3-day tropical storm.
Member Since: Posts: Comments:
NICyclone,
You skipped Delta lol


Oops! i knew i had missed one!!!
Member Since: Posts: Comments:
I just found out about TD 13 and since this depression is going to move in many directions and very slowly I expected a larger area of tropical storm warnings


or are the models in better agreement now?
Member Since: Posts: Comments:
Quoting KoritheMan:


Well, the trailing weakness is forecast to be pretty far south, so I would say Louisiana is pretty much in the crosshairs either way.

There is still the possibility that it comes farther westward though, barring a center reformation.


Thanks Kori
Member Since: Posts: Comments:
2241. Patrap
Quoting muddertracker:

You can have ours! Texas will happily hand it over..


Sw La and Central La are in Drought beaucoup.
Member Since: July 3, 2005 Posts: 424 Comments: 128344
More I look at this pathetic system, the more I don't see it making landfall anytime soon, might sit all weekend
Member Since: Posts: Comments:
Quoting Drakoen:


93L..13L...whatever you wanna call it isn't even close to being a tropical depression.


Post-season analysis should be interesting.
Member Since: Posts: Comments:
Quoting dsenecal2009:
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.
You'd have to be near Bayou Liberty for rain to be much of an issue in Slidell.

Unless there is somewhere that street-flooding gets in houses that I don't know about...
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting TXCaneCrasher:
Question, if the COC does form further to the South, will the approaching trough still pull it inland over Louisiana or will the High out West be able to pull it slightly towards Texas? Just curious. Thanks in advance


I think that the trough will still pull it. The only effect would be more time over water which would translate into more strenghtening, and the landfall spot being moved to the east perhaps as far east as NOLA which is not the best case scenario. The other option which is not as likely is that it does not get pulled by the Trhough and it lingers in the GOMEX even longer, and perhaps eventually move towards Mexico in a wsw motion. Texas has a very persistent ridge anchored in place. This stubborn Ridge will deflect storms sp as far as the ridge is there TX will remain dry unfortunately, and winter is fast approaching, which by the way will be a La Niña winter similar to last winter.
Member Since: Posts: Comments:
Quoting Drakoen:


93L..13L...whatever you wanna call it isn't even close to being a tropical depression.


"Isn't even close" is a bit dramatic. While it may not be a tropical depression by the book, it's certainly close. We have a closed low with organized convection on one side. Yeah, it's still sort of broad, but it's close.
Member Since: July 15, 2006 Posts: 17 Comments: 10250
Quoting Patrap:


Yeah,,maybe a Drought will show up.

You can have ours! Texas will happily hand it over..
Member Since: Posts: Comments:
Quoting TXCaneCrasher:
Question, if the COC does form further to the South, will the approaching trough still pull it inland over Louisiana or will the High out West be able to pull it slightly towards Texas? Just curious. Thanks in advance


Well, the trailing weakness is forecast to be pretty far south, so I would say Louisiana is pretty much in the crosshairs either way.

There is still the possibility that it comes farther westward though, barring a center reformation.
Member Since: Posts: Comments:
Quoting Drakoen:


93L..13L...whatever you wanna call it isn't even close to being a tropical depression.


Well, the National Hurricane Center declared it, so officially, it is.
Member Since: July 6, 2010 Posts: 113 Comments: 32072
2232. Patrap



Member Since: July 3, 2005 Posts: 424 Comments: 128344
Quoting Patrap:


Yeah,,maybe a Drought will show up.


lol
Member Since: Posts: Comments:
Does Katia look any better to the trainned eyes on here or is she still getting sheared and sucking in dry air.
Member Since: Posts: Comments:
2229. Patrap
Quoting RitaEvac:


Voodoo magic may now play a hand into this. Never tempt nature or Voodoo for that matter...lmao


Yeah,,maybe a Drought will show up.
Member Since: July 3, 2005 Posts: 424 Comments: 128344
2227. Drakoen
Quoting MississippiWx:
I don't think TD13 is a textbook tropical depression either, but there is a reason why the NHC doesn't ask us to classify systems.


93L..13L...whatever you wanna call it isn't even close to being a tropical depression.
Member Since: October 28, 2006 Posts: 57 Comments: 30494
Quoting stormpetrol:
Katia looks to be trucking WNW now.
OMG from you? LOL
Member Since: Posts: Comments:
Quoting MississippiWx:
I don't think TD13 is a textbook tropical depression either, but there is a reason why the NHC doesn't ask us to classify systems.


Yup, exactly my thinking.
Member Since: Posts: Comments:
Quoting Patrap:
Takes a surge event to Bust a Levee been the rule ,,this aint gonna be one.


Voodoo magic may now play a hand into this. Never tempt nature or Voodoo for that matter...lmao
Member Since: Posts: Comments:
For Katia the convection has lifted further N because of the shear. However the COC is still on the NHC track. With her weakening it may drift further W then currently expected.

Member Since: Posts: Comments:
Quoting DFWjc:


here ya go. Link


Thats the one! to funny i just saw cantorie's long range forcast for katia and that song poped in my head
Member Since: Posts: Comments:
2220. IKE

Quoting muddertracker:


I thought they were all fixed and "updated"...right?
Not sure...think so.....
Member Since: Posts: Comments:
Quoting Levi32:


It's amazing what proximity to land can do to the NHC's reasoning. To some extent it makes sense, but that would never be classified anywhere else.

levi now that the nhc came out with their track are you going to change your single loop track or keep it for now?
Member Since: Posts: Comments:
Quoting IKE:
Here's hoping none of the levees break.....

http://www.youtube.com/watch?v=U9cpziwfV90&fe ature=related


5 day QPF.....




I thought they were all fixed and "updated"...right?
Member Since: Posts: Comments:
I don't think TD13 is a textbook tropical depression either, but there is a reason why the NHC doesn't ask us to classify systems.
Member Since: July 15, 2006 Posts: 17 Comments: 10250
Quoting justsouthofnola:
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
That's partly what I'm worrying about...
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting Patrap:


Anytime tonight thru whenever seems.





Thank you Pat
Member Since: Posts: Comments:
2214. Patrap
Takes a surge event to Bust a Levee been the rule ,,this aint gonna be one.
Member Since: July 3, 2005 Posts: 424 Comments: 128344
2213. Drakoen
Quoting nrtiwlnvragn:


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.
Quoting Levi32:


It's amazing what proximity to land can do to the NHC's reasoning. To some extent it makes sense, but that would never be classified anywhere else.


Agree.
Member Since: October 28, 2006 Posts: 57 Comments: 30494
Quoting HCW:


Xtrap is never wrong :)


I don't care how we get rain. I just paid $105 for round bales of hay. We need RAIN!!!!!!!!
Member Since: Posts: Comments:
Quoting nolacane2009:
When should we expect all of the Heavier rain Pat?

radar can tell you that - go to noaa.gov enter new orleans, la - see the radar screen - click on that and then click on the looping radar -
green is mild rain - watch for the red/yellow...
Member Since: Posts: Comments:
Models and experts have no clue what this is gonna do, not listening to anybody or anything
Member Since: Posts: Comments:
2208. DFWjc
Quoting mrpuertorico:
I am going to sing the doom song now.. doom doom du du doom doom doom doom --- Gir (from invader zim)


here ya go. Link
Member Since: Posts: Comments:
Quoting tvengineer8:

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 :-) )





Great work tv8..keep Bob on the air please, he's the best thing going in NOLA!
Member Since: Posts: Comments:
2206. Patrap
Quoting Drakoen:


2 feet of rain? Have the boat ready (seriously).



I can walk the Levee of the Miss to The COE Headquarters
Member Since: July 3, 2005 Posts: 424 Comments: 128344
Quoting CybrTeddy:
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)
Tropical Storm Tammy (October)
Hurricane Whitney (October)
Tropical Storm Alpha (November)
Tropical Storm Beta (November/December)
Probably gonna see more than that in October...especially since this has been a home brew year. Who knows though, like you said, this type of forecasting is nearly pointless lol.
Member Since: Posts: Comments:
2204. GetReal
Member Since: July 4, 2005 Posts: 204 Comments: 8874
Question, if the COC does form further to the South, will the approaching trough still pull it inland over Louisiana or will the High out West be able to pull it slightly towards Texas? Just curious. Thanks in advance
Member Since: Posts: Comments:
2202. IKE
Here's hoping none of the levees break.....

http://www.youtube.com/watch?v=U9cpziwfV90&fe ature=related


5 day QPF.....


Member Since: Posts: Comments:
2201. Drakoen
Quoting Patrap:


2 feet of rain? Have the boat ready (seriously).
Member Since: October 28, 2006 Posts: 57 Comments: 30494
I am going to sing the doom song now.. doom doom du du doom doom doom doom --- Gir (from invader zim)
Member Since: Posts: Comments:
2199. Levi32
Quoting Drakoen:
I mean... LOL



It's amazing what proximity to land can do to the NHC's reasoning. To some extent it makes sense, but that would never be classified anywhere else.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting HurricaneDean07:
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)


You skipped Delta lol
Member Since: Posts: Comments:
2197. Patrap
Member Since: July 3, 2005 Posts: 424 Comments: 128344
Quoting 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.


That is NOT good news.
Member Since: Posts: Comments:
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.
Member Since: September 23, 2005 Posts: 14 Comments: 11179

Viewing: 2245 - 2195

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Mostly Cloudy
73 °F
Mostly Cloudy