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 midgulfmom:
Perhaps showing us the track?...LOL


lol! well, he is a smart one ;)
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Quoting NoVaForecaster:
Poll Time!

Which AOI becomes Lee?

A. 93L
B. 94L
C. Something Else

Which AOI becomes Maria?
A. 93L
B. 94L
C. Something Else

Which is more of a threat to the US?

A. 93L
B. Katia
C. 94L
D. None

93L:


94L:


Katia:


I say B,A,A
BBA
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A Darkening Dvorak in the Eastern GOM and some curved banding as well.

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Member Since: August 19, 2006 Posts: 13 Comments: 14451
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Quoting IKE:

Joe Bastardi
The storm in the gulf is
3-5 days of problems. US models have no clue.. last night taking it
into Mexico, now taking into the lower ms vly


Yesterday's 12Z ECMWF had Southern Texas, last night's 00Z ECMWF near New Orleans, so it is not just the US models, but Bastardi would never let that fact obscure his hatred for NOAA.
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Quoting hurricanehanna:

my little Morkie was running circles in the kitchen this am...never done that before...
Perhaps showing us the track?...LOL
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Yep --- although there are more checking in than cancelling at this time.
Quoting IKE:

Already huh?

Member Since: July 10, 2005 Posts: 157 Comments: 29383
386. jpsb
Quoting want2lrn:
It appears we are going to miss out on this rain event here on the central Texas coast, again. I think what happened to Don has scared his brother Lee.......
pay little attention of the models right now, things are changing fast, once (if) a closed low forms then look to the models.
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Quoting uptxcoast:
Just on observation...This morning not a cloud in the sky in Houston, now a number of cumulus clouds are forming, don't see much lift to them but keeping my fingers crossed.


I'm seeing that too. Temperatures are much nicer as well...
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Quoting CaneHunter031472:


My Boxer was telling me this morning that it's a bit too early to tell, but that she was going to keep an eye on it and would let me know ASAP.


Now, when my Springer starts "nesting" I know something is happening...
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17:25:00Z 27.633N 87.883W 648.5 mb
(~ 19.15 inHg) 3,824 meters
(~ 12,546 feet) 1009.9 mb
(~ 29.82 inHg) - From 115° at 23 knots
(From the ESE at ~ 26.4 mph) 8.2°C
(~ 46.8°F) 4.6°C
(~ 40.3°F) 23 knots
(~ 26.4 mph) 40 knots
(~ 46.0 mph) 3 mm/hr
(~ 0.12 in/hr) 40.0 knots (~ 46.0 mph)
Tropical Storm
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Note the Radar Filling in as 93L gets some meat on His Bones this afternoon.


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dollar higher on crude already
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379. SLU
000
ABPZ30 KNHC 011137
TWSEP

MONTHLY TROPICAL WEATHER SUMMARY
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM PDT MON AUG 1 2011

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

OVERALL TROPICAL CYCLONE ACTIVITY IN THE BASIN DURING JULY WAS
SLIGHTLY BELOW NORMAL. THREE TROPICAL STORMS FORMED...AND TWO
BECAME HURRICANES...WITH DORA REACHING MAJOR HURRICANE STRENGTH. ON
AVERAGE THREE TO FOUR TROPICAL STORMS FORM IN THE BASIN DURING JULY
...WITH TWO REACHING HURRICANE INTENSITY AND ONE BECOMING A MAJOR
HURRICANE.

REPORTS ON INDIVIDUAL CYCLONES...WHEN COMPLETED...ARE AT THE WEB
SITE OF THE NATIONAL HURRICANE CENTER...USE LOWER-CASE LETTERS...
HTTP://WWW.NHC.NOAA.GOV/2011EPAC.SHTML

NAME DATES MAX WIND (MPH)
-------------------------------------------------
MH ADRIAN 7-12 JUN 135
H BEATRIZ 19-22 JUN 90
H CALVIN 7-10 JUL 80
MH DORA 18-24 JUL 155
TS EUGENE 31 JUL- 45


$$
HURRICANE SPECIALIST UNIT




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378. IKE

Quoting Beachfoxx:
Cancellations are coming in...
People are deciding not to come for the weekend.  : (

Already huh?
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376. SLU
000
ABNT30 KNHC 011154
TWSAT

MONTHLY TROPICAL WEATHER SUMMARY
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT THU SEP 1 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SEVEN NAMED STORMS AND A TROPICAL DEPRESSION FORMED IN THE ATLANTIC
BASIN DURING THE MONTH OF AUGUST. ONE OF THESE STORMS WAS MAJOR
HURRICANE IRENE THAT IMPACTED MUCH OF THE EAST COAST OF THE UNITED
STATES. THE NUMBER OF NAMED STORMS WAS WELL ABOVE THE LONG-TERM
(1944-2010) AVERAGE OF FOUR...BUT THE NUMBER OF HURRICANES...TWO...
WAS BELOW THE AVERAGE. IN TERMS OF ACCUMULATED CYCLONE ENERGY...
ACE...WHICH MEASURES THE COMBINED STRENGTH AND DURATION OF TROPICAL
STORMS AND HURRICANES...TROPICAL CYCLONE ACTIVITY WAS ABOUT AVERAGE.

REPORTS ON INDIVIDUAL CYCLONES...WHEN COMPLETED...ARE AT THE WEB
SITE OF THE NATIONAL HURRICANE CENTER...USE LOWER-CASE LETTERS...
HTTP://WWW.NHC.NOAA.GOV/2011ATLAN.SHTML

SUMMARY TABLE

NAME DATES MAX WIND (MPH)
------------------------------------------------- ---
TS ARLENE 29 JUN-1 JUL 65
TS BRET 17-22 JUL 65
TS CINDY 20-22 JUL 60
TS DON 27-30 JUL 50
TS EMILY 1-7 AUG 50
TS FRANKLIN 12-13 AUG 45
TS GERT 14-16 AUG 60
TS HARVEY 19-22 AUG 60
MH IRENE 20-28 AUG 120
TD TEN 25-26 AUG 35
TS JOSE 28-29 AUG 45
H KATIA 29 AUG- 75

$$
HURRICANE SPECIALIST UNIT


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Quoting hurricanehanna:

my little Morkie was running circles in the kitchen this am...never done that before...


My Boxer was telling me this morning that it's a bit too early to tell, but that she was going to keep an eye on it and would let me know ASAP.
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Quoting nash28:


Afternoon Press.


Hey, mon! What's up?
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FYI... HH

Product: NOAA High Density (HDOB) Message (URNT15 KWBC)
Transmitted: 1st day of the month at 17:30Z
Date: September 1, 2011
Aircraft: Lockheed WP-3D Orion (Reg. Num. N42RF)
Mission Purpose: Investigate seventh suspect area (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 08
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Quoting aimetti:


Well its not like hes lying. Im not a big fan of his but it "could" threaten the east coast.
he did good with irene
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HH data:

17:25:00Z 27.633N 87.883W 648.5 mb
(~ 19.15 inHg) 3,824 meters
(~ 12,546 feet) 1009.9 mb
(~ 29.82 inHg) - From 115° at 23 knots
(From the ESE at ~ 26.4 mph) 8.2°C

pressure dropping?

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93L Floater - Rainbow Color Infrared Loop

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Quoting hurricanejunky:
There is a RIDICULOUS amount of convection filling the Eastern GOM!
I wouldn't mind if some of that made it onshore in West FL.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting HCW:
Models have gone bonkers!
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Quoting midgulfmom:
My critter report: South of N.O., Due North of Grand Isle...chorus of croaking frogs, black ants in the kitchen and cats hiding under the house.. What does this portend? LOL

my little Morkie was running circles in the kitchen this am...never done that before...
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Just on observation...This morning not a cloud in the sky in Houston, now a number of cumulus clouds are forming, don't see much lift to them but keeping my fingers crossed.
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thats a Cane

HOUR: 96.0 LONG: -92.63 LAT: 29.65 MIN PRESS (hPa): 976.48 MAX SURF WIND (KNOTS): 67.28
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There is a RIDICULOUS amount of convection filling the Eastern GOM!
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Quoting NoVaForecaster:


Oh no... 2 more storms possible... TWC is gonna go crazy over this one....
In all likely hood Lee would become the GOM disturbance & Maria the one NE of Bermuda based on those percentages.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
93L 12Z GFDL


HOUR: .0 LONG: -89.17 LAT: 25.60 MIN PRESS (hPa): 1009.35 MAX SURF WIND (KNOTS): 29.83
HOUR: 6.0 LONG: -89.80 LAT: 26.31 MIN PRESS (hPa): 1006.07 MAX SURF WIND (KNOTS): 39.15
HOUR: 12.0 LONG: -90.77 LAT: 27.07 MIN PRESS (hPa): 1002.79 MAX SURF WIND (KNOTS): 44.78
HOUR: 18.0 LONG: -91.80 LAT: 27.14 MIN PRESS (hPa): 1000.58 MAX SURF WIND (KNOTS): 38.56
HOUR: 24.0 LONG: -92.20 LAT: 27.64 MIN PRESS (hPa): 1000.19 MAX SURF WIND (KNOTS): 35.39
HOUR: 30.0 LONG: -92.40 LAT: 27.90 MIN PRESS (hPa): 997.57 MAX SURF WIND (KNOTS): 33.21
HOUR: 36.0 LONG: -92.60 LAT: 27.96 MIN PRESS (hPa): 995.85 MAX SURF WIND (KNOTS): 34.53
HOUR: 42.0 LONG: -92.74 LAT: 28.02 MIN PRESS (hPa): 994.24 MAX SURF WIND (KNOTS): 33.59
HOUR: 48.0 LONG: -92.60 LAT: 28.37 MIN PRESS (hPa): 992.14 MAX SURF WIND (KNOTS): 42.12
HOUR: 54.0 LONG: -92.11 LAT: 28.72 MIN PRESS (hPa): 988.59 MAX SURF WIND (KNOTS): 41.27
HOUR: 60.0 LONG: -91.92 LAT: 29.40 MIN PRESS (hPa): 982.09 MAX SURF WIND (KNOTS): 60.57
HOUR: 66.0 LONG: -92.46 LAT: 29.77 MIN PRESS (hPa): 975.79 MAX SURF WIND (KNOTS): 70.51
HOUR: 72.0 LONG: -92.56 LAT: 30.10 MIN PRESS (hPa): 977.55 MAX SURF WIND (KNOTS): 58.92
HOUR: 78.0 LONG: -92.82 LAT: 30.20 MIN PRESS (hPa): 979.54 MAX SURF WIND (KNOTS): 54.12
HOUR: 84.0 LONG: -92.87 LAT: 30.02 MIN PRESS (hPa): 978.67 MAX SURF WIND (KNOTS): 65.68
HOUR: 90.0 LONG: -92.97 LAT: 29.70 MIN PRESS (hPa): 977.46 MAX SURF WIND (KNOTS): 62.73
HOUR: 96.0 LONG: -92.63 LAT: 29.65 MIN PRESS (hPa): 976.48 MAX SURF WIND (KNOTS): 67.28
HOUR:102.0 LONG: -92.07 LAT: 29.77 MIN PRESS (hPa): 976.46 MAX SURF WIND (KNOTS): 65.47
HOUR:108.0 LONG: -91.14 LAT: 30.24 MIN PRESS (hPa): 977.74 MAX SURF WIND (KNOTS): 61.18
HOUR:114.0 LONG: -90.46 LAT: 30.90 MIN PRESS (hPa): 981.91 MAX SURF WIND (KNOTS): 52.24
HOUR:120.0 LONG: -89.87 LAT: 31.96 MIN PRESS (hPa): 986.48 MAX SURF WIND (KNOTS): 45.30
HOUR:126.0 LONG: -89.19 LAT: 32.73 MIN PRESS (hPa): 989.46 MAX SURF WIND (KNOTS): 37.33

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P451 thanks for that explanation, it really helps novices like myself see and understand things a bit better.

Like with any Hurricane that's still that far out to sea, it's wait and see what develops. I just hope it stays out to sea for all concerned, including passing by Bermuda.
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357. jpsb
Quoting cloudburst2011:



25N AND 89W IS WHERE THE coc is FORMING
If you are correct on that she is going to have a long time over water.
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Quoting midgulfmom:
My critter report: South of N.O., Due North of Grand Isle...chorus of croaking frogs, black ants in the kitchen and cats hiding under the house.. What does this portend? LOL


Locusts and grasshoppers moving up here.


Doom portends,,

But as long as I can see the Game tonight we'll be okay.
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Quoting cdo13:
First post ever here....hopefully that large area of convection in the Gulf will move west.


My second time to post here and I second your

post! Bring it to TX!
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Juan was a flooder fo sure.

Had coffins popping out the crypts in Lafitte South of here.

Messy Halloween it was.
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Quoting tropicfreak:
P451, that is some strong vorticity with 94L, I think we may be looking at Lee now.

850 mb

I wonder if the Hurricane Hunters find a close low with 93L & some west winds which they would designate first? I got 93L as Lee & 94L as Maria. See what they do at 5PM.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Cancellations are coming in...
People are deciding not to come for the weekend.  : (
Quoting 69Viking:


Dan I just hope the tourists know to stay out of that mess this weekend or we're going to have a few drownings. High Surf and strong rip current advisories have already been issued.

Member Since: July 10, 2005 Posts: 157 Comments: 29383
Quoting presslord:
Well, well, well....Wadda we have here?!


Afternoon Press.
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My critter report: South of N.O., Due North of Grand Isle...chorus of croaking frogs, black ants in the kitchen and cats hiding under the house.. What does this portend? LOL
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Quoting Ineluki:


Joe B. said a storm could threaten the East Coast?!

Pardon me while I lie down from the shock.

(Yes, of course Katia's path isn't set in stone for anywhere yet, but c'mon, it's Joe B. That's the only prediction he can make.)


Well its not like hes lying. Im not a big fan of his but it "could" threaten the east coast.
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Quoting EYEStoSEA:


That is such a nice tribute, TTom....and thank you for all you do :)


I have to agree. You do good work.
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346. IKE

Joe Bastardi
whats 2,000 miles among friends. I like a 3-5 day loop de loop like juan in 1985, then a move northeast......


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It appears we are going to miss out on this rain event here on the central Texas coast, again. I think what happened to Don has scared his brother Lee.......
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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.