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
Reader Comments
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September: 6 named storms
October: 4 named storms
November: 2 named storms
December: 1 named storm??
Total: 24 named storms.
I don't have one, but want one!!!! :(
LOL LOL LOL!!! +100000000
Will keep it for now....loop could be very small and it would kind of look like one sweeping track, but who knows lol. We shall see.
I'm off to dinner and class for the evening. Later all.
Brown must have slipped Avila one.
I've heard there are some areas that flood with moderate rainfall (3-5")..my guess is you would be safe to leave in the morning.
Thanks Cane, I live on the Middle Texas Coast and this is the driest I have ever seen it. Not wishcasting for anything serious. Just would like a little rain every now and then
Tea just came out of my nose hilarious
lol
lol!!!
..ooofh
Anyway, the southern Apps could also use rain from future Lee.
Like I said, I don't believe it's a TD yet either, but it's certainly closer than you're stating.
You what I kinda agree with ya, basically what I was thinking!
What mixes with Fresca?
hahaha
Southern Comfort, ice..
Beautiful beach weather Tuesday but the surf started getting bad yesterday and today is really bad!
A couple of girls some dave mathews and bucket of fried chicken :D
I guess we will agree to disagree and leave it at that.
Now that is hilarious!!!! LOL!!
* Louisiana has declared a state of emergency.
Looking at rainbow loop for TD13... anyone hazard a guess where the center is...
Maybe I missed that part of the discussion... just trying to see what everything will try to spin around.
Is that it maybe around 25.5N 88.5W?
Looking at the NHC lat/long I'm wondering if it's relocating.
Trust me, we are still recovering here in Mississippi, not fully recovered yet, but in much better shape. I wish I had better news for the folks in TX, but this is the way I see it. The problem Texas is having is fully related to that very stron ridge on top of the state, and having another La nina winter will only mean that the dry weather will persist perhaps until 2012 Spring or even the Summer. Still it is worth to watch what will happen with potential Lee, but my fear is that even if for some reason Lee moved towards Texas it would evaporate just as Don did in the beginning of the season. I love Texas and you are all in my prayers. BTW our next president will be from there lol.
can't afford all that...i'll stick with the southern comfort and ice...
New 0 Z
Link
I'm not trying to be rude, 451 or Drak, or anybody for that matter, but the NATIONAL HURRICANE CENTER declared it as a tropical depression. That means it IS a tropical depression, no matter what you think (Again, not being rude).
If you want to know
Whats
The
Forecast.
Just keep watching.
Thanks to you both. There will most certainly be at least minor flooding here, and I think my little cottage might take some water. Live about 75' off of Gause Blvd. We had a couple inches of sporadic downpours and drizzle today up to Pearl River, and the streets were hazardous even then. Cannot imagine what peak 3-5 inches an hour will do on top of a weekend-long storm.
I've seen blizzard watches before there was a blizzard. I've seen tornado watches before there was a tornado (by definition actually)... Why can't they issue tropical watches before there is an actual storm?
If that is indeed true... Seems like the classic definition of beuracracy to me... Procedures and policies getting in the way of common sense...
Huh? The fires? Leaking BP oil rig? The large cluster of thunderstorms in the gulf? Nagin's back?
I think the NHC would rather "have told them so" and it didn't happen tban "wish they had said something" and it did happen. They don't put out advisories for invests so this was probably the best way to get the word out to the public about a potentially damaging rain event starting very soon in a vulnerable area.
... That's a really terrible pun ...
I haven't tried Fresca before, I might give it a shot sometime.
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