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
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 — Blog Index
The system in the gulf may come in to play and may pull Katia more West than the models show
Hey Will. Hope she just completely misses the east coast.
I read the model wrong it actually takes it on a straight track into SW LA then back south then basically due east right along the coast then NE into SE La..that would really suck
lol... I am actually having a good laugh tonight. It feels a heck of a lot better than being frustrated. :)
Also, I think distributed computing has a huge potential to help out the computer models. if you've ever used SETI@Home or Folding@Home, you are familiar with it. Imagine millions of private computers crunching model data continuously, 24/7... Model resolution could be bumped exponentially and models could be updated more frequently as well. Imagine the GFS Ensemble creating a mean track out of 200,000 variable runs, not just 20.
...must study. Dang tropics.
I hate it when they clip like this in the evenings.
May I say...95L?
*Click on graphics to magnify (Graphics can further be magnified in Link window by clicking on them)
Link?
ty Tex we sure dont want her here. But im still wishing for Tex to get some much needed rain
Ugh...I know! That was also annoying during IRENE too....
Well at least we don't have a solar storm now, that would completely knock out the satellites, right?
To be on the safe side, I'll say pre-95L. :P
These still impress me, they're practically broadcast quality. Most excellent indeed.
Lol. Yes it does! I'm giving up frustration tomorrow. :D
some hurricane irene aftermath from a location near me
I understand that feeling. I could read some out of Al Cotton's Advanced Inorganic Chemistry, or... I could not.
Thanks Will. :) We'll take all the good wishes we can get!
Any thoughts regarding my observation?
wow...12z 251k
Thank you very much! There are actually pretty easy to make once the main "template" is done.
It's way too early for that.
Lol...That run of the CMC isn't complete yet...It goes from 12z Saturday to 0z Saturday.
Well...I don't know about that...but I have some serious heartburn tonight that's keeping me up....
Looks like you need PEPTO and I need some ANTACID or something...LOL...
Goes out to 12z Monday.Run's already completed out to 144 hours.How on earth do you move a whole tropical cyclone (84 to 96 hours) down the coast from New Orleans to Brownsville in 12 hours? I mean, I guess it makes sense, but it just feels like CMC is missing something there in the middle.
HOWEVER...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.
Well I know one thing...if there was a weather-betting Casino in Vegas (which I seriously doubt there is)...my money's on that become 95L....
And in said Casino...consequences of a bad forecast are probably worse than eating crow....
could possibly but too early to tell how close each would be for that to happen
Nah, not under this current set up.
Viewing: 3151 - 3195
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 — Blog Index