Gulf of Mexico disturbance 93L a Lousiana flood threat; Katia a hurricane

By: Dr. Jeff Masters , 3:28 PM GMT on September 01, 2011

Share this Blog
26
+

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

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 845 - 795

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 | 64Blog Index

Quoting Levi32:
I should also really point out a big slip in terminology that is working its way into the blog. I am guilty of it as well sometimes in my videos. We can't say that a "recurving storm" means one that is missing land. That is entirely incorrect. In fact, the majority of storms that hit North America ARE recurving. The question should be whether the storm will hit land as it recurves, not whether it will recurve. Most storms do recurve into the mid-latitudes, and that can occur over the ocean or over land.

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.
Member Since: Posts: Comments:
Quoting HCW:
93L 18z model runs from the NHC

Mash it




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!
Member Since: Posts: Comments:
Levi

A big shift west with the European model for Katia...your thoughts

Quoting Levi32:


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.
Member Since: Posts: Comments:
I would rather get the rain to Texas without a hurricane thanks.
Member Since: Posts: Comments:
Quoting oldgranddad:
Quoting Levi32:


Yeah unfortunately. It could happen, but the timing would have to be perfect and everything. We're in the pattern of the 1950s. You've heard me and others mention it regarding more than one kind of weather pattern. Here it's the dryness in Texas. The mid-1950s was a perpetual drought period for that area.


I recall the 50s in fact, it wasn't until later that century we even had proper names. But I remember that bitch Hazel, in fact, we called her "that bitch". No offense to the women folk here or the youngster, but god damn, she was f. . . g bitch. Still makes me wet my pants thinking of her. But I do that even in best times.


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.
Member Since: Posts: Comments:
thanks Levi! you are so nice to teach me like this. I have learned a lot from you.

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
Member Since: Posts: Comments:
No thanks, Katia needs not to pull an Ike!! We in SETX dont need that scenario again.
Member Since: Posts: Comments:
I should also really point out a big slip in terminology that is working its way into the blog. I am guilty of it as well sometimes in my videos. We can't say that a "recurving storm" means one that is missing land. That is entirely incorrect. In fact, the majority of storms that hit North America ARE recurving. The question should be whether the storm will hit land as it recurves, not whether it will recurve. Most storms do recurve into the mid-latitudes, and that can occur over the ocean or over land.
Member Since: Posts: Comments:
Quoting HoustonTxGal:
What the heck do we have to do here in Texas to get some rain?  Do we need to ship it in from the New England area, god knows they have more water than they can deal with.

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.
Member Since: Posts: Comments:
835. HCW
93L 18z model runs from the NHC

Mash it


Member Since: Posts: Comments:
Weather question of the week (at least for Texas): What will Invest 93L do? Will bring any rain to those of us on the west side of the TX/LA border? Or will the "Texas Shield" push it away, or maybe even do to it what it did to Don? It's a waiting game, no matter how you slice it. My fingers are crossed for a rain-maker.
Member Since: Posts: Comments:

Quoting trHUrrIXC5MMX:

wait!, you will get your big slice soon


From your lips to god's ears.. eveything is dead or dying here. Lakes are dry, my and everyone elses yard is dust, most of my trees are dead or dying.. it is so sickning


Member Since: Posts: Comments:

Katia might be tryin for a comeback
Member Since: Posts: Comments:
Quoting katadman:
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
Member Since: Posts: Comments:
there is always next yr
Member Since: Posts: Comments:
Quoting bythegraceofgod:
Anyone know how long Camille sat in the gulf before coming onshore in Gulfport? I had heard it sat there a while. Just thinking...


Camille hit Cuba first... not really anything like this one.
Member Since: Posts: Comments:
Quoting kshipre1:
Levi,

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?


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.
Member Since: Posts: Comments:
Maybe Katia might pull off Ike?

Member Since: Posts: Comments:
As we speak, Katia is plunging West at 18mph and as it continues to do so, the models will keep shifting west. This is getting me worried...
Member Since: Posts: Comments:
Quoting HoustonTxGal:
What the heck do we have to do here in Texas to get some rain?  Do we need to ship it in from the New England area, god knows they have more water than they can deal with.

wait!, you will get your big slice soon
Member Since: Posts: Comments:
Quoting katadman:
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


Me too....but only on my work pc
Member Since: Posts: Comments:
Quoting wunderweatherman123:

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 :(


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.
Member Since: Posts: Comments:
any ATCF data?
Member Since: Posts: Comments:
What the heck do we have to do here in Texas to get some rain?  Do we need to ship it in from the New England area, god knows they have more water than they can deal with.
Member Since: Posts: Comments:

man if another el nino formed a less active hurricane season :D and RAIN FOR TEXAS :D
Member Since: August 23, 2011 Posts: 0 Comments: 1728
Quoting Levi32:


Yeah unfortunately. It could happen, but the timing would have to be perfect and everything. We're in the pattern of the 1950s. You've heard me and others mention it regarding more than one kind of weather pattern. Here it's the dryness in Texas. The mid-1950s was a perpetual drought period for that 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!
Member Since: Posts: Comments:
Quoting BrockBerlin:


They better not steal Lee for this storm, Lee is a name that means business.... Maria sounds like nothing.

(Also I preseason predicted Lee would be retired, although hopefully that won't come to pass).


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!
Member Since: Posts: Comments:
Quoting MississippiBoy2:
does this mean it will just sit there?


Yup, most likely through the weekend before eventually making a move, which I think will be northeast for the end-game.
Member Since: Posts: Comments:
Quoting katadman:
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
Changing the filter to "Show All" finally fixed it for me and I'm stuck with IE here at the office.
Member Since: Posts: Comments:
Quoting nrtiwlnvragn:
Katia TVCN shifted quite a bit west for one model cycle

12Z
AL 12 2011090112 03 TVCN 168 319N 641W



18Z
AL 12 2011090118 03 TVCN 168 291N 710W

Yes indeed...12z vs 18z:

Member Since: Posts: Comments:
Levi,

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?
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting angiest:

The fifties (I can't remember the exact years) remain the worst overall drought on record in Texas.

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.
Member Since: Posts: Comments:
few days over warm water 93 could become very heavy its already big
Member Since: Posts: Comments:
A interesting trend in the models for Katia, the UKMET and ECMWF have shifted considerably southward, however the ECMWF suddenly shifts it away from the US coast line. This could be a very interesting situation setting up. CMC is also quite far south that it has been. Keep a close eye on Katia while we're watching 93L/Lee in the GOMEX.
Member Since: Posts: Comments:
Quoting Levi32:


Temporarily yes it should move WNW, but then it runs into a wall. See the high over OK, AR, and MO? That's going to stay pressed south as the shortwave over the northwestern U.S. comes east. That should block any northwest movement of 93L after tomorrow.

does this mean it will just sit there?
Member Since: Posts: Comments:
Quoting Levi32:


The "neutral" this summer was a ruse... the PDO is negative and the atmosphere never stopped behaving like a strong La Nina was in play. Essentially we're heading for a 3rd-year La Nina. It won't officially be La Nina again until we have a 3-month period where Nino3.4 SST anomalies average -0.5C or lower. It will probably take another year or so and a transition into a weak El Nino to really cure the Texas drought.

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 :(
Member Since: August 23, 2011 Posts: 0 Comments: 1728
Quoting katadman:
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
It's usually due to an image that was posted. What version of IE are you using? Since upgrading to 9 the issue seems to have resolved itself. Also, you can try changing the comments viewed from say 100 to 50 so the image will rotate out faster.

Hope that helps!
Member Since: Posts: Comments:
Quoting thedawnawakening3:
UKMET model 12z run is a reason why we can't let our guard down on Katia.

Also it points the picture in which the wave near 29w/8n will move into the Caribbean Sea with it so far south and the high strong enough.


This is true, though I have reservations about it having Katia moving south of the high between herself and "Lee." Also, it's worth pointing out that the UKMET was a horrible southerly outlier with Irene.
Member Since: Posts: Comments:
We don't need another hurricane for 2011 because inland NC between I-95 and the coast is pretty damaged badly. Gov. Perdue requested 2 more counties to be added to disaster list today.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting xtremeweathertracker:

Levi your thoughts on the models moving 93L north when steering currents at least temporarily should take it northwest!


Temporarily yes it should move WNW, but then it runs into a wall. See the high over OK, AR, and MO? That's going to stay pressed south as the shortwave over the northwestern U.S. comes east. That should block any northwest movement of 93L after tomorrow.

Member Since: Posts: Comments:
796. IKE

Quoting MiamiHurricanes09:
As Brock pointed out a little earlier, the UKMET has shifted quite a bit to the south with Katia.

93L in line with other models.
Member Since: Posts: Comments:
UKMET model 12z run is a reason why we can't let our guard down on Katia.

Also it points the picture in which the wave near 29w/8n will move into the Caribbean Sea with it so far south and the high strong enough.
Member Since: Posts: Comments:

Viewing: 845 - 795

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 | 64Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Overcast
39 °F
Overcast

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron