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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Hope that helps!
i understand and i know its WAY FAR OUT to make any calls whatsoever but is there a chance a moderate el nino will form for the 2012 season which makes the activity in the atlantic slow like 09 and 06 and possibly end the drought. the latest CFS models still have a moderate weak la nina by april so i have a feeling el nino wont be forming anytime soon :(
The 2011 drought is by far the worst single-year one in Texas--far worse, that is, than any that occurred during the 1950s (or any other period). The current drought is affecting a wider area, and it's been more profound, with much hotter temperatures, less precipitation, and drier soil. Of course, the 1950s multi-year drought lasted longer; it remains to be seen whether the current will continue long enough to surpass the old one(s). FWIW, Texas State Climatologist Dr. Nielsen-Gammon says that that Texas is "likely to be" at the start of a multiyear drought.
good afternoon. two quick questions. First, how much stock do you put in the UKMET shifting Katia a bit more south and west? Second, is there any relationship between La Nina, ENSO neutral and recurving of storms?
I mean, during ENSO neutral seasons, are there less recurves compared to La Nina?
Yes indeed...12z vs 18z:
Yup, most likely through the weekend before eventually making a move, which I think will be northeast for the end-game.
My wife's name is Maria, trust me we don't need a storm named Maria in the Gulf when we live near the coast in NW Florida! Yikes, my friends would never let me down if a TS or Hurricane named Maria hit our area!
It hasn't been this dry here since 1933 and August was the hottest in Texas since they kept records. The situation in Texas is a lot worse than the nation thinks it is but it will eventually start hitting the pocket books of many. Cattle owners are having to sell off their breeding stock at cheap prices because they can't feed them due to lack of good hay crops. At first, the price of meat will be cheaper but eventually it will really start to sky rocket because the supply won't be there.
The drought in Texas has already reached 5 billion dollars and it's only going to get worse...maybe much worse. And the general public across the nation is oblivious to just how bad it is but they'll find out soon. Cotton products will be higher, along with beef and poultry. Get ready!
man if another el nino formed a less active hurricane season :D and RAIN FOR TEXAS :D
Maybe....it's hard to sustain La Ninas after 2 years. We might be in for a solid 3-year La Nina like in the 1950s which would mean next year will stay cold to neutral, but there's no way to know. What we did know was that this La Nina or cold period in general was likely to last a long time, and it has.
Me too....but only on my work pc
wait!, you will get your big slice soon
UKMET is an outlier right now and reflects the danger of the pattern, but it was a very bad southerly outlier during Irene, and thus I don't trust it very much at this moment for the Cape Verde trackers.
Neutral years are funny things that are different creatures depending on what conditions preceded them. 2005's neutral was very different from this year's neutral. Thus, it depends. Some years with very robust La Ninas, like 2007, hold storms so far south that all they do is track through the Caribbean, which is why we had Dean and Felix that year. At that point there is very little recurving going on.
Camille hit Cuba first... not really anything like this one.
Can someone explain why the blog is so narrow on my screen? It cuts off the text on the right side of the longer posts. I have opened the blog in IE, Mozilla and Chrome. Same format in all. Anyone have a remedy? TIA
mine is doing the same thing...very frustrating
Katia might be tryin for a comeback
Mash it
I dunno, ask Dallas what they did. They're the only ones not in exceptional drought.
I still stand by my hope we'll get a Hermine II before too much longer. Everything is set up for it, just need an EPAC pop-up that suddenly feels a poleward urge.
I just might take up meteorology in school because of you! weather and tropical cyclones have always fascinated me ever since I was a kid
something else that happened in the 50's was increased frequency of tropical systems effecting the mid-Atlantic and New England.... particularly 1954 and 1955.
A big shift west with the European model for Katia...your thoughts
Looks like models are finally not quite as spagetti, my friend already has a hurricane party planned..yea..we live in lafayette..right in the middle of the jumble!
True. Recurvature doesn't and shouldn't necessarily imply that no land will be affected. In fact, if it weren't for recurving storms, we here on the west coast of Florida wouldn't see nearly so many strikes.
The 94L number really ought to justify a Tropical Depression at 5pm. And the ambiguous result for Katia will probably keep it as a hurricane in the next advisory; they're really loath to downgrade until it's crystal clear that it's necessary, particularly when they'd just have to reupgrade again.
Again it reflects the danger of the pattern with a tendency for ridging north of Katia's area over southeast Canada. I still think she'll pass between Cape Hatteras and Bermuda, but one must always be wary of a Dora-type track in such patterns. I think it's unlikely here, but folks should still watch the storm and not forget about it.
Kind of looks like a doctor's signature huh?
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