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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Or this. Maybe your wife is just mindful of a pattern of behavior. ;)
per doc masters, I would say he was about 24 hours late
(click for full size)
3km moving nest, from: http://storm.aoml.noaa.gov/hwrfxprojects/?project Name=HFIP Demo 2010
Katia will definitely help boost the ACE...right now she has only contributed roughly 3, but if she attains major hurricane status she will probably produce up to 25-30 or so.
Nice to meet all the NOLA people on here tonight.. I am in 70119 also.. my street only flooded about 2 1/2 feet for Katrina (Esplanade ridge) and my driveway is a couple of feet above the street so I think I should be ok with my cars at home..
Don't think there is anything stopping you from parking on the roof of the old Schwegmans on Broad and Beinville.
Now.. I will have to be at work thru most of the bad weather and where work is is one of the lowest spots in the city (Jeff Davis and Euphrosine).. wonder if I can get my car into the elevator and up to the second floor :-)
(Yes.. I will be keeping BOB on the air throughout the storm :-) )
(blue, right-center)
From the Horse's mouth, and I quote;
"SINCE THE DEPRESSION IS IN ITS FORMATIVE STAGE THE INITIAL MOTION
IS HIGHLY UNCERTAIN. IN FACT...THE CENTER COULD REFORM WITHIN THE
LARGE CIRCULATION DURING THE NEXT 12-24 HOURS. THE DEPRESSION IS
CURRENTLY LOCATED TO THE SOUTH OF A MID/UPPER LEVEL RIDGE OVER THE
CENTRAL UNITED STATES. THE RIDGE IS FORECAST TO SLIDE EASTWARD AND
WEAKEN DURING THE NEXT 2-3 DAYS...LEAVING THE CYCLONE IN WEAK
STEERING FLOW. THE OFFICIAL FORECAST SHOWS A SLOW NORTHWESTWARD
MOTION DURING THE NEXT 24 HOURS...FOLLOWED BY A TURN TOWARD THE
NORTH AND NORTHEAST. THE NHC TRACK IS IN BEST AGREEMENT WITH THE
GFS AND ECMWF MODELS".
The 3pm SJU NWS discusion, which can be found on my blog, says that the next system after katia and any system from africa in the next 7 to 14 days will be a major threat for the antilles and caribbean its actually a good little read.
I'll be watching for relocations to the south in subsequent updates... The more that happens, the worse it is for everyone along whichever strand of spaghetti this thing chooses to follow.
Lee: Category 1: 80 Mph; September
Maria: Tropical Storm: 50 Mph
Nate: Category 4: 140 Mph
Opheilia: Category 3: 115 Mph
Phillipe: Tropical Storm: 65 Mph
Rina: Category 2: 105 Mph
Sean: Category 4: 150 Mph
Tammy: Category 1: 90 Mph; October
Vince: Tropical Storm: 70 Mph
Whitney: Category 2: 110 Mph
Alpha: Tropical Storm: 50 Mph
Beta: Category 3: 115 Mph; November
Gamma: Tropical Storm: 60 Mph
Epsilon: Category 1: 75 Mph
Season Aftermath:
25 NS
11 Hurricanes
5-6(Depending on if Katia becomes Major)
Agreed. I don't think the situation was urgent enough where they couldn't wait until the organization improved.
Anytime tonight thru whenever seems.
Let's go XTRAP!! Verify, baby...Texas is counting on ya..lol!
Sometimes you do things to make sure people are paying attention.
$64,000 ? I really don't know to be honest. I think the jury is still out on Katia
Xtrap is never wrong :)
That may be right for crops, etc but not the ground water problems. Run off will fill back in some of the city water supplies & wells etc. Give the livestock something to drink! It might not soak the ground as it should but even run off would be a godsend for many places. People are moving off their land because thier wells are dry. Anything is better than nothing.
NEXRAD Radar
Type
Velocity Azimuth Display Wind Profile ° Elevation
Range
124 NMI
Hurricane Maria (September)
Hurricane Nate (September)
Tropical Storm Ophelia (September)
Hurricane Rina (September)
Hurricane Sean (October)
Hurricane Tammy (October)
Hurricane Whitney (October)
Tropical Storm Alpha (November)
Tropical Storm Beta (November/December)
Looks to me over LA at 31N and 92W
But it certainly could move under the heaviest convection..
I think there is a combination of the two. As conditions start to improve for development (if they do as forecasted) I dare to say that the COC will be relocated to the SE of where it is right now, but I am hoping this is not the case. As Levi said in the Barometer Show, If Lee is still over water by Monday chances are it will be a Hurricane.
Was active on here last year, very nice to see some familiar names here. Stay safe ladies and gentlemen.
Certainly not consistent with the standards they have applied to previous systems. They are doing an in-house experiment this year which could lead to issuing watches/warnings before formation in the future. Of course that will leave another area for criticism.
That is NOT good news.
You skipped Delta lol
It's amazing what proximity to land can do to the NHC's reasoning. To some extent it makes sense, but that would never be classified anywhere else.
2 feet of rain? Have the boat ready (seriously).
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