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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As of a matter of fact, I lived in Texas for several years, so I know how it would go...
Texas does not need that much rain, sorry to tell ya ;)
Yep everywhere around here after Rita. That's what happened to my mobile home. Yeah, I know all the jokes. Lol. 90 ft oak went smack down the middle. Didn't break one window but blew the walls out broke the steel frame under the house, went to the ground. Looked like a giant hotdog with a lot of relish on it. Lol. Ah memories. :)
1. will Katia noodles trend more to the west?
2. will 93l move more to the east??
Baptist Hospital, or other parking high space
TA13, when you are watching your cattle and horses die and your crops are dead and there are bills to pay... Even if it floods, it'll help. If no rain, this drought could continue until next March even. More deaths, more people losing their homes and way of living. Not to mention the fires that are increasing and getting harder and harder to put out.
Link
A 40mph storm, not warm core, that formed 60 wiles west of Bermuda and moved due North is not that much of a threat. My point was that it seems the TPC is in a hurry sometimes to name something just for the sake of issuing a name.
Thanks :)
Texas can't win either way :(
Omaha? ;)
wunderful,..not
thats what I was looking at
The 19-20 inch bomb is a bit speculative though, as Allison demonstrated, certainly possible.
Where I am at ... I'd take it. Other people sure would not. Of course, it doesn't look like it is coming here anyway.
I think that one is a "possible" caribbean cruiser!
not a wind event
but...
lot of rain about to be over my house
Or use Adblock. ;)
Im depressed now
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.
;-)
AMEN TO THAT!!
Me too...and Jr. as well.
Left in March...I wish Texas had rain too, but not heavy rain, not for a long time, like what would occur. Light to steady rain for several days... :)
I'm in South Florida. Personally, I have no immediate concerns, it's just something i'm watching.
..well dats not good
I can tell you some places in Mid-City that I know won't flood, they didn't after Katrina....but uptown my knowledge is not great. Elevated parking garage is always good, in the CBD or there is a large lot on North Rampart off the Quarter.
Haha, I deserve that. I ask because this city has limited parking as is...let alone "high" parking. I parked my car in Loyola's parking lot before Cindy and got a big fat ticket.
So..I was hoping for a no-ticket type of location ;)
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.
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.
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