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: 2945 - 2895

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

LOOKS like 25N 89W is the new LLC
Member Since: Posts: Comments:
Quoting GTcooliebai:
I'm thinking somewhere in that convective mess around 25 N 87W.


There is no vorticity there according to surface observations. With all due respect, I do not think the center will reform there. Not to mention, that would be a very sizable jump -- over 200 miles. I've never seen such a drastic center reformation.
Member Since: Posts: Comments:
well, if TD13 develops further south, then that gives is more space to grow and more time over water to strengthen..lovely..
Member Since: Posts: Comments:
night everyone, back maybe briefly in the morning.
Member Since: Posts: Comments:
2941. Drakoen
lol some of you guys need to step away from the blog. Wash down a prozac or valium with some Fresca.
Member Since: Posts: Comments:
Quoting extreme236:
Looking on the Nasa satellite images, almost looks like Katia has a warm spot on IR.
I definitely see what you're alluding too, and it matches rather closely to where the circulation appears to be on shortwave. Gonna keep watching for persistence though.



Damn, I should probably be sleeping by now, but the tropics are better than sleep...anything is better than sleep haha.
Member Since: Posts: Comments:
Quoting ConnecticutWXGuy:


lol and that statement you are reacting to coming from somebody with MET at the beginning of their name. hmmmm


Lol...Good point.
Member Since: Posts: Comments:
Quoting KoritheMan:


I knew you were pretty damned knowledgeable, but I never suspected you were an actual met. You should try and get a job with the NWS in NOLA. :)
Well, we do some contract work for NOAA, NASA, Navy, and, sometimes, NWS NOLA (actually in Slidell, 2 miles from the office), outside of private, commercial clients.

I could get a job at NWS, but have no real desire to. What I do is more diverse than daily forecasting, which I enjoy.
Member Since: Posts: Comments:
Quoting atmoaggie:
Still enjoying this spaghetti model plot...



As accurate as any other at this point, IMO.


HAHAHA! That is hilarious. I have been thinking the same thing for the past 24 hours lol
Member Since: Posts: Comments:
Quoting ConnecticutWXGuy:


lol and that statement you are reacting to coming from somebody with MET at the beginning of their name. hmmmm
what could MET mean of a weather Forum, maybe Meteorologist.
Member Since: Posts: Comments:
2934. JLPR2
Katia is feeling it.
Member Since: Posts: Comments:
If the center relocates south, then that would only spell nothing but trouble as far as intensification goes.
Member Since: Posts: Comments:
2932. JNCali
Quoting jpsb:
The Texas Rain Shield is forecast to be with us thru next summer. With luck we might get some rain this winter with northers, maybe.

Just want to make sure.. you guys have all washed your cars and started painting your houses right?? That almost always brings the moisture
Member Since: September 9, 2010 Posts: 5 Comments: 1032
Quoting atmoaggie:
Well, when you are a met and you are hosting an outdoor party for ~45 people at your house on this particular weekend, the phone rings constantly...
wait are you having a met party?
Member Since: Posts: Comments:
2930. GetReal
Quoting TampaSpin:
Channel 2 Loop seems to show a nice LLC developing with TD13 much further South than NHC has it currently!


Would that be near 25N and 90W???
Member Since: Posts: Comments:
Quoting Huracaneer:

Can't make heads or tails of the mess in the Gulf, some folks here are pretty good at finding centers in developing systems. Where do you think the center is located?
I'm thinking somewhere in that convective mess around 25 N 87W.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
2928. Skyepony (Mod)
ADT has a bit of a jump SE with TD13.

Time Final/MSLPLat/Vmax Fnl Adj Ini Cnstrnt Wkng Rpd Cntr Mean Scene EstRMW Storm Location Fix
Date (UTC) CI MSLP /BiasAdj/(kts) Tno Raw Raw Limit Flag Wkng Region Cloud Type (km) Lat Lon Mthd Comments
2011SEP02 001500 2.0 1009.0/ +0.0 / 30.0 2.0 2.0 2.0 NO LIMIT OFF OFF 16.04 -9.49 SHEAR N/A 26.64 91.45 FCST
2011SEP02 004500 2.0 1009.0/ +0.0 / 30.0 1.9 1.9 1.0 0.1T/hour ON OFF 18.34 -7.77 SHEAR N/A 26.73 91.54 FCST
2011SEP02 011500 2.0 1009.0/ +0.0 / 30.0 1.9 1.9 1.0 0.1T/hour ON OFF 19.34 -3.51 SHEAR N/A 26.82 91.63 FCST
2011SEP02 014500 2.0 1009.0/ +0.0 / 30.0 1.9 1.9 1.0 0.1T/hour ON OFF 19.94 2.61 SHEAR N/A 26.90 91.71 FCST
2011SEP02 021500 2.0 1009.0/ +0.0 / 30.0 1.9 1.9 1.0 0.1T/hour ON OFF 19.44 6.06 SHEAR N/A 26.98 91.80 FCST
2011SEP02 024500 2.0 1009.0/ +0.0 / 30.0 1.9 1.8 1.0 0.1T/hour ON OFF 18.84 8.78 SHEAR N/A 27.06 91.87 FCST
2011SEP02 031500 2.0 1009.0/ +0.0 / 30.0 1.8 2.0 2.1 0.1T/hour ON OFF 18.84 -6.77 SHEAR N/A 26.63 91.53 FCST
Member Since: Posts: Comments:
Well, if the center were to relocated (not saying it will) under that burst of convection in the central Gulf that could be trouble for the West Coast of Florida. I remember back in the 90's (yes I realize that models back then were primitive or non-existent) that Roy Leep form Channel 13 was talking about some disturbed weather in the Gulf. That night I wake up to Tropical Storm Force winds! Did not last long, but it surprised the heck out of me.
Member Since: Posts: Comments:
2926. beell
Quoting atmoaggie:
beell, where is your dmin/dmax chart?



it appears to be east of the Sabine River...
Member Since: Posts: Comments:
Quoting JLPR2:


Africa keeps producing.
One of those is suppose to develop
Member Since: Posts: Comments:
IT definatly seems TD 13 is reloating the the Central Gulf, further southeast.
Member Since: Posts: Comments:
2923. JGreco
Quoting TampaSpin:
Channel 2 Loop seems to show a nice LLC developing with TD13 much further South than NHC has it currently!



That is what I was seeing. My local Met also mentioned that the coc looks to be reforming South.
Member Since: September 22, 2005 Posts: 0 Comments: 322
Still enjoying this spaghetti model plot...



As accurate as any other at this point, IMO.
Member Since: Posts: Comments:
Quoting KATRINABILOXIGIRL:
I was speaking of when they take off from Keesler. Wasn't sure where they were gonna be taking off from tonight.

The planes they used from MS during Irene took off from TLIA near Pascagoula.
Member Since: July 24, 2008 Posts: 0 Comments: 156
Quoting MississippiWx:


I beg your pardon. I haven't been staring at a satellite all day either. I have work/school as a college student. I didn't say anything snooty to you, so why the smarta## remark?


lol and that statement you are reacting to coming from somebody with MET at the beginning of their name. hmmmm
Member Since: Posts: Comments:
Td 13 is really starting to consolidate a little bit more now that shear looks to have abaited a bit...looks to be starting to fire thunderstorms around the Center
Member Since: Posts: Comments:
Late evening,

Why isn't 94L Maria? If they classified Jose...this isn't Maria?...LOL

Anyway, very interesting evening you all probably have been having talking about TD 13 and Katia....
Member Since: Posts: Comments:
2917. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 163 Comments: 52100
Quoting atmoaggie:
Umm, yeah?
(Really?)

I usually don't throw it around in the blogs, so I can see how some may not be aware.


I knew you were pretty damned knowledgeable, but I never suspected you were an actual met. You should try and get a job with the NWS in NOLA. :)
Member Since: Posts: Comments:
2915. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 163 Comments: 52100
Looking on the Nasa satellite images, almost looks like Katia has a warm spot on IR.
Member Since: Posts: Comments:
Channel 2 Loop seems to show a nice LLC developing with TD13 much further South than NHC has it currently!
Member Since: Posts: Comments:
Quoting GTcooliebai:
Yeah, I saw that, the big question is what if any impacts will Lee have on her Path??? And I think it will depend on how strong Lee gets, can't rule out a Fujiwhara here if they get close enough.
I don;t see Lee making out of the Gulf, across land and staying intact as a TC.
Member Since: Posts: Comments:
Quoting HurricaneDean07:
Mississippiwx, Get the troll spray! and get in the Troll proof dome! theyre mobbing us!!! RUN FOR THE HILLS...
lol, just ignore the trolls Mississippiwx


Yeah, for real. Lol. I didn't think that guy was a troll, though. Oh well.
Member Since: Posts: Comments:
2910. GetReal
Member Since: Posts: Comments:
Quoting KoritheMan:


Wait, you're a meteorologist atmo?
Umm, yeah?
(Really?)

I usually don't throw it around in the blogs, so I can see how some may not be aware.
Member Since: Posts: Comments:
Quoting TomTaylor:
at the time, the downgrade was well justified


Katia was very much a tropical storm for most of the day.
Member Since: Posts: Comments:
Mississippiwx, Get the troll spray! and get in the Troll proof dome! theyre mobbing us!!! RUN FOR THE HILLS...
lol, just ignore the trolls Mississippiwx
Member Since: Posts: Comments:
looks even more apparent of a different coc now..... almost hurricane like

Link
Member Since: Posts: Comments:
Quoting TampaSpin:



NHC downgraded Katia to a Tropical Storm.......that is UNREAL looking at Satellite.......HUM
at the time, the downgrade was well justified
Member Since: Posts: Comments:
Quoting MississippiWx:


The crazy thing is that 24 inches isn't really exaggerating. :-/


Heh. I am using my survival of storms like Juan in 1985, Frances in 1998, and Allison in 2001 as consolation I'll survive Lee. :P
Member Since: Posts: Comments:
Quoting atmoaggie:
Well, when you are a met and you are hosting an outdoor party for ~45 people at your house on this particular weekend, the phone rings constantly...


Wait, you're a meteorologist atmo?
Member Since: Posts: Comments:
Quoting KoritheMan:


At this point I'd rather take strong winds than heavy rain. I'm not liking the forecast of 24 inches of rain near New Orleans.


The crazy thing is that 24 inches isn't really exaggerating. :-/
Member Since: Posts: Comments:
2901. jpsb
Quoting atmoaggie:

Do not let your pump just run and run if you are getting no water pressure. Shut it off until someone that knows what they are doing can prime it.


+1000
Member Since: Posts: Comments:
Quoting WhoDat1:
local met, here in south la seems to think we might have 2 seperate systems in the gulf


My grandmother was telling me this too, but I don't see it.

Perchance, do you know who the meteorologist was that said this?
Member Since: Posts: Comments:
2899. JGreco
Quoting MississippiWx:


I beg your pardon. I haven't staring at a satellite all day either. I have work/school as a college student. I didn't say anything snooty to you, so why the smarta## remark?


Just poof him...he's obviously a troll.
Member Since: September 22, 2005 Posts: 0 Comments: 322
Quoting TomTaylor:
yea, I wasn't sure what you meant by that. Thanks for clearing that up.

And wow that's a long time to be on the phone
Well, when you are a met and you are hosting an outdoor party for ~45 people at your house on this particular weekend, the phone rings constantly...
Member Since: Posts: Comments:
the 00z out yet?
Member Since: Posts: Comments:
Quoting louisianaboy444:


If it slides any further east maybe not if it slides further west then maybe more so...kinda in the middle right now...its interesting that the storm just sits right on the coast just south of me for almost a day though...that would keep us with almost 24 hour nasty weather


At this point I'd rather take strong winds than heavy rain. I'm not liking the forecast of 24 inches of rain near New Orleans.
Member Since: Posts: Comments:
2895. KEEPEROFTHEGATE (Mod)
Tropical.Cyclone.Formation.WARNING
013/TD/L/CX
MARK
25.95N/89.91W


Member Since: July 15, 2006 Posts: 163 Comments: 52100

Viewing: 2945 - 2895

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 JeffMasters

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