Gulf of Mexico disturbance 93L a Lousiana flood threat; Katia a hurricane
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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TS.Katia's_12amGMT_ATCF : Starting 1Sept_12amGMT and ending 2Sept_12amGMT
The 4 eastern line-segments represent TropicalStormKatia's path
and the westernmost line-segment is the straightline projection.
Using straightline projection of the travel-speed&heading derived from the
ATCF coordinates spanning the 6hours between 6pmGMT then 12amGMT :
TS.Katia's travel-speed was 17.5mph(28.2k/h) on a heading of 297.5degrees(WNW)
TS.Katia was headed toward passage over Sebastian,Florida ~4days20hours from now
Copy&paste 14.8n43.6w-15.1n45.2w, 15.1n45.2w-15.3n46.9w, 15.3n46.9w-15.8n48.6w, 15.8n48.6w-16.5n50.0w, vrb, 15.8n48.6w-27.793n80.455w into the GreatCircleMapper for more info
The previous mapping (for 1Sept_6pmGMT)
I don't know how they knew that there are 4 kids living here, but, to all of you on this blog that are members of the Red Cross, Emergency Response Teams, and other humanitarian groups I want to thank you all. Those Mickey Mouse dolls brought the first smile to my 2 year old twin girls faces that I have seen in nearly a week, that was priceless.
IN THE LONG RANGE...A STRONG MID-LEVEL TROUGH IS FORECAST TO DEVELOP OVER THE GULF OF MEXICO AS THE ATLANTIC SUBTROPICAL RIDGE BUILDS WESTWARD. THIS PATTERN SHOULD FORCE KATIA ON A MORE WEST-NORTHWESTWARD MOTION BY THE END OF THE FORECAST PERIOD
UPDATE...THE MAIN STORY THIS EVENING IS THE DEVELOPMENT OF TD
13 IN THE NORTHERN GULF. THE OFFICIAL FORECAST HAS THE SYSTEM SLOWLY
DEVELOPING INTO TROPICAL STORM LEE AND MOVING SLOWLY IN A NORTHWARD
DIRECTION INTO SOUTHERN LA OVER THE WEEKEND. AT THIS TIME...THE MAIN
RISK FOR OUR CWA WILL BE WITH HEAVY RAINFALL. THIS FITS THE
CONCEPTUAL MODEL FOR A SLOW MOVING TS/TD AND IF CERTAIN ELEMENTS
PLAY OUT...THE RAINFALL WILL NOT BE JUST HEAVY...IT COULD BE
EXCEPTIONAL! AT THIS POINT...WILL STAY CONSERVATIVE ON THE TOTALS
AND KEEP THE HEAVIEST AND THE FOCUS ACROSS THE SOUTH HALF WITH THE
POTENTIAL FOR 3-10 INCHES.
Which One?
Just a tad looks to go right over Vermillion bay and Lafayette Parish
But seriously, I'll be so glad when the "Texas Rain Shield" finally goes away.
2011SEP02 001500 3.6 995.8 57.0 2.9 2.8 2.8 NO LIMIT ON FLG -62.56 -56.78 UNIFRM N/A N/A 16.38 49.87 FCST GOES13 34.6
2011SEP02 011500 3.6 995.8 57.0 2.9 3.4 3.5 0.5T/hour ON OFF -73.36 -64.95 IRRCDO N/A N/A 16.45 50.07 FCST GOES13 34.4
2011SEP02 014500 3.6 995.8 57.0 3.0 3.4 3.8 0.5T/hour ON OFF -74.36 -74.07 UNIFRM N/A N/A 16.49 50.17 FCST GOES13 34.4
2011SEP02 021500 3.6 995.7 57.0 3.1 3.4 4.3 0.5T/hour ON OFF -73.36 -76.35 UNIFRM N/A N/A 16.64 50.44 FCST GOES13 34.2
exactly
She will most likely be a hurricane in the morning.
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.
We could use some of that in GA as well. I thought Irene might give us something, but all she gave us was a tease of a 15-minute squall...
I can usually hear them when they take off!
your showing us a black box you can see it we cant
??? strange.
If they take off from Tampa like they did earlier today, you will have to have super hearing. :-)
You're welcome to join me in the rain dance. The more the merrier. We've tried almost everything else, may as well try this.
TD13
I'm still kind of thinking central Louisiana as a landfall target myself.
What a lovely post..brings tears to my eyes..good luck. Hopefully your pump will be working tomorrow.
I know sorry Taz...I couldn't get it to load.
Sure is, but Katia isn't.
Thanks, I have someone coming tomorrow morning to look at it. My husband is in Albany on business so I am just winging it.
Yeah me2 I'm thinking more from Jeff Davis Parish to Lafayette parish i agree it will turn North or maybe North North East but i dont think that trough will be that strong to pull it NE that sharply IMO
There's 9 million gallons of raw sewage below Omaha tonight because it rained like hell after it snowed like hell.
Vermont just lost all of their plumbing, In Omaha, they get 'soft-ball hail". The "Okie-Texas Drought" jumps off the scale.
The Peterman glacier is about to lose twice as much ice as it lost last year. ........
Giant Chunk of Greenland Ice Set to Break Away
http://www.ouramazingplanet.com/giant-chunk-of-gr eenland-ice-set-to-break-away-1960/
thats ok
map is filling up
got less than 90 days left now of the 2011 atlantic hurricane season
we could still see another eight to ten storms
My comment should have been about the potential vorticity inversion my friend keeps talking about. (He's a phunny guy, but a former PhD student of Bill Gray's)
Still haven't fully grasped all that he was talking about. I'm looking for papers on it, but the notion seems to be an obscure one...
Here is a small one: http://ams.confex.com/ams/pdfpapers/21588.pdf
Might want to check the NHC site. :-)
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