Little change to TD 7; 93L may develop off the coast of Africa

By: Dr. Jeff Masters , 1:57 PM GMT on August 10, 2012

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Tropical Depression Seven continues westward across the central tropical Atlantic with little change in appearance. Looking remarkably like the tropical depression that became Tropical Storm Ernesto last week, TD 7 has a limited region of heavy thunderstorms, as seen on satellite loops. A large amount of dry air to the west and north is visible on water vapor satellite loops, and this dry air is interfering with TD 7's heavy thunderstorms. Wind shear is a light 5 - 10 knots, which is favorable for intensification. Ocean temperatures are 26.5°C, which is a bit on the cool side, but these temperatures are 0.5° warmer than on Thursday. Winds at the Middle Atlantic buoy 41041 peaked at 29 mph, gusting to 38 mph, at 1:50 am EDT this Friday morning, when the center of TD 7 passed about 40 miles to the south. TD 7 will pass about 60 miles south of buoy 41040 near midnight tonight. The first hurricane hunter mission into TD 7 is scheduled for Saturday morning.


Figure 1. Morning satellite image of TD 7.

Forecast for TD 7
TD 7 formed about 400 miles east-northeast of where Ernesto became a tropical depression, as seen on our wundermap. Atmospheric and oceanic conditions are currently quite similar to what Ernesto experienced, and I expect TD 7 will struggle with dry air like Ernesto did. The SHIPS model predicts that shear will remain light through tonight, then rise to the moderate range on Saturday, when the storm will encounter upper-level southwesterly winds associated with a trough of low pressure. However, ocean temperatures will warm to 28°C, which may partially counteract the increase in shear, as far as maintaining a favorable environment for development. Dry air and shear may be significant enough to destroy TD 7 on Sunday, as predicted by the GFS and ECMWF models. These models tried to kill off Ernesto in a similar situation last week, so I am inclined to believe TD 7 will survive for the coming five days, but struggle. The official NHC forecast of a 45 mph tropical storm moving through the Lesser Antilles Islands Saturday night and Sunday is a reasonable one.


Figure 2. Morning satellite image of Invest 93L.

93L
A strong tropical wave in the far Eastern Atlantic that emerged off the coast of Africa Thursday night was designated Invest 93L by NHC. In their 8 am Tropical Weather Outlook, NHC gave 93L a 50% chance of becoming a tropical depression by Sunday morning. Satellite loops show a pronounced spin to the atmosphere at mid levels, but little in the way of heavy thunderstorm activity. The latest Saharan Air Layer Analysis from the University of Wisconsin shows that while the atmosphere immediately surrounding the disturbance is moist, there is a large area of dry air from the Sahara to the west and north. This dry air will be a significant impediment to development during the coming week. The ECMWF model shows some weak development of 93L over the coming week, and predicts a general west-northwesterly track. The storm may be something Bermuda needs to be concerned about in eight or so days.

I'll have a new post this afternoon.

Jeff Masters

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Quoting kmanislander:


Good morning

Given that for many years I have always been referred to on this blog as "Kman" I wonder if you could find another abbreviation for Wunderkidcayman ?? :-)

TIA


Alrighty then.........."WKman".....
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Quoting DavidHOUTX:


This one went quite a long way too!



true but the ones i showed started before of south of CV Islands
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the dynamic models show a much more westward track which is strange because of all the possible recurving talk. i guess any track is probable.
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THE REMNANTS OF ERNESTO ARE EXPECTED TO MOVE OFF MEXICO INTO THE
EASTERN PACIFIC WITH THE POTENTIAL TO BECOME A TROPICAL CYCLONE. IF
THIS IS THE CASE...IT WILL ACQUIRE A NEW DEPRESSION NUMBER...OR A
NEW NAME IF IT BECOMES A TROPICAL STORM.
Member Since: April 23, 2011 Posts: 104 Comments: 14873
Quoting SLU:
TD 7 getting better organized


Was about to mention that... is trying to get some heavier convection around its center. Well see how it fairs the rest of the day.
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TD-7 RGB Loop

Member Since: July 3, 2005 Posts: 428 Comments: 129841
Quoting sar2401:


Kman, you might be right, and I'll hop on board that train if TD7 starts to slow down. At 19 mph forward speed, both the shear and trades get magnified as potential problems for development.

How are you doing this morning, BTW?


Good morning

Given that for many years I have always been referred to on this blog as "Kman" I wonder if you could find another abbreviation for Wunderkidcayman ?? :-)

TIA
Member Since: August 19, 2006 Posts: 0 Comments: 15948
Quoting AussieStorm:


Long track CV Systems.












This one went quite a long way too!

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thanks for posting these. I guess there are cases where some cv storms do make it far west but the conditions in the upper atmosphere have to be almost perfect.
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Thanks Dr.M and have a good weekend. The Blog is quiet today. Ernesto wore a lot of folks out and looking like the same general type of situation for the next several days. Interesting looking at the recent loops that the limited convection with TD7 appears to be relocating a little bit to the Northern edge of the depression closer to 13N. If this trend continues, and it does in fact survive dissipation like predicted by old reliable (GFS) I would expect the models to shift a bit to the North in the coming days.


As for 93L: This dry air will be a significant impediment to development during the coming week.

That pretty much tells the whole story for the next several days as to both systems.
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Quoting VR46L:


I am liking 93L as Gordon , being a bit of a gambler I would bet on it
Seems more likely all though T.D 7 has a head start.I need them both to be named so they can move the hell out of the way and make room for Isaac.
Member Since: August 14, 2010 Posts: 10 Comments: 17810
Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Friday, August 10th, with Video


Levi,nice update, right at the moment the environment out in the Atlantic is too friendly for these waves coming off Africa.Lots of dry air to battle and the trade winds out there cause them to fly across the Atlantc.The tropics look active,but not too friendly out there for these storms.
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12z Early Cycle NHC model tracks
Invest93

Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Dynamic Models (More sophisticated models)




Early Model Wind Forecasts

Member Since: July 3, 2005 Posts: 428 Comments: 129841
TD7 is to slow down near 60W unlike Ernesto which sped up when it reached 60W
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Quoting Tribucanes:
Blog will see a steady increase over the next two weeks as this starts to get very interesting. Gotta go, have a great day everyone. What were the comment totals per day during Katrina? Thanks to whomever answers.


Have a good day. I don't know the exact figures for blog counts during Katrina but updates were pretty frequent, so it never got as bad as I thought it might, I do remember one time when the comments were over 5,000 before Dr. Masters did an update. I'm sure the total comments must have been near 100,000 though.
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He can still retain his name as long his mid level circulation going
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Quoting Levi32:


I put an annotation on the video mentioning the audio problem and apologizing. Supposedly everyone should be able to see that message. Lately it's one thing or another that I forget before turning the recorder on that has been giving audio issues.
does the overall pattern favor the US getting weak systems due to the el nino?
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Quoting washingtonian115:
Thanks Doc..and good morning blog...I'm not surprised T.D 7 is struggling.I mean why do you think they're called depressions?.They're depressed in this stage it's just that some get over it faster than others,and it appears T.D 7 still hasn't recovered.Maybe today It'll decide to move on and be Gordon..


I am liking 93L as Gordon , being a bit of a gambler I would bet on it
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TD 7

Member Since: July 3, 2005 Posts: 428 Comments: 129841
Quoting kshipre1:
i am sure most everyone in here remembers hurricane frances back in 2004 which made landfall on the east coast of florida. The lat lon coordinates at which it started in the atlantic made it easier to cross westward and hit the CONUS. That and coupled with the atlantic high and less troughs. 93L has a good chance to go westward but chances of recurving at some point could be likely due to very few cv storms making it that far west at once. Nonetheless, it should be interesting to watch.


Long track CV Systems.










All September Hurricanes
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52. SLU
...ERNESTO DISSIPATES OVER SOUTHERN MEXICO...HEAVY RAIN THREAT CONTINUES...
------------------------------------------------- -------------------------------

10:00 AM CDT Fri Aug 10
Location: 18.0°N 99.2°W
Moving: W at 15 mph
Min pressure: 1005 mb
Max sustained: 25 mph

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Quoting sar2401:


Thanks, Levi. I don't know if it's my crummy laptop speakers or what, but your volume is very low as I watching the video. I tend to agree with your analysis on both TD7 and 93L. TD7 seems unlikely to make it to the eastern Caribbean as anything more than a remnant low, but your comments about the upper level circulation are definitely an issue. The Yucatan Straits were pretty well worked over by Ernesto, so an intact UL circulation from TD7 might give us a surprise as it gets to that area.


I put an annotation on the video mentioning the audio problem and apologizing. Supposedly everyone should be able to see that message. Lately it's one thing or another that I forget before turning the recorder on that has been giving audio issues.
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Caribe wave flaring today! Hey Gro! Does it rate "blob" status yet?
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Ernesto dissipated... he's not gonna keep his name. :(
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ok, thanks Levi. so, in short, you think home grown storms could be more a threat. I was just asking becuase a lot of forecasters said we are in enso but heading into el nino.

Also, not to focus only on Florida, but do you see this year as possibly having tracks similar to 2004 and 2005? If I am recalling correctly, 2004 was a weak to moderate el nino and 2005 was an enso season.

Thanks Levi.
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Quoting sar2401:


Kman, you might be right, and I'll hop on board that train if TD7 starts to slow down. At 19 mph forward speed, both the shear and trades get magnified as potential problems for development.

How are you doing this morning, BTW?

also TD7 should slow down by 60W
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Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Friday, August 10th, with Video


Thanks, Levi. I don't know if it's my crummy laptop speakers or what, but your volume is very low as I watching the video. I tend to agree with your analysis on both TD7 and 93L. TD7 seems unlikely to make it to the eastern Caribbean as anything more than a remnant low, but your comments about the upper level circulation are definitely an issue. The Yucatan Straits were pretty well worked over by Ernesto, so an intact UL circulation from TD7 might give us a surprise as it gets to that area.
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Not enough water in Mississippi River to float steamboat
Published: Friday, August 10, 2012, 9:20 AM





Catherine Threlkeld, The Times-Picayune
The Mississippi River is low on the levee in New Orleans. Upriver, the American Queen steamboat is docked in Memphis, unable to continue its trip because of low water.


MEMPHIS, Tenn. — The American Queen steamboat is docked in Memphis, unable to paddle on down the Mississippi River because of low water.


A trip that began Aug. 3 at Louisville, Ky., was cut short well before the steamboat's destination of Vicksburg, Miss.

American Queen Steamboat Company's Tim Rubacky tells The Commercial Appeal navigation problems caused by sluggish river flow make it unwise for the Queen to go any further south than Helena, Ark. The decision to lay up at Memphis was made after talking with the Coast Guard and the Army Corps of Engineers.

About 58 passengers remained aboard Thursday night. About 240 others went on to Vicksburg by bus.
Low water levels in the Mississippi are the result of a combination of high temperatures and lack of rain and snow further north of Memphis.
Member Since: July 3, 2005 Posts: 428 Comments: 129841
44. SLU
TD 7 getting better organized
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Blog will see a steady increase over the next two weeks as this starts to get very interesting. Gotta go, have a great day everyone. What were the comment totals per day during Katrina? Thanks to whomever answers.
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Quoting kwgirl:
Good morning all. There seems to be something brewing off of CA in the central Caribbean that is causing me concern. The satelitte images seem to indicate that the protective death ridge is moving which will allow a door into the GOM. I hope I am reading this incorrectly and encourage anyone on here to give me their opinion. Nothing we can do about it, but if a storm starts heading my way, I am going to the Grotto to pray for intervention.
My locals here in Texas last night said the ridge was expected to build and the GOM would be closed for buisness for a while. I don't think they really know. Kind of a bold statement to make.
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Thanks Doc..and good morning blog...I'm not surprised T.D 7 is struggling.I mean why do you think they're called depressions?.They're depressed in this stage it's just that some get over it faster than others,and it appears T.D 7 still hasn't recovered.Maybe today It'll decide to move on and be Gordon..
Member Since: August 14, 2010 Posts: 10 Comments: 17810
Quoting ncstorm:


Ha..thats what I figure but I had to ask..thanks!

No problem. When is takeoff?
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Quoting kshipre1:
hey levi. hows it going? good to see you and hope school is going well. are we already in an el nino season? or we are transitioning into one? it seems that even in the la nina years past couple of seasons, trade winds and dry air were a lot more than should have been. what do you make of that and what do you forsee higher chances of landfalling cyclones in the south versus storms going out to sea? thanks Levi. look forward to your insight. have a nice day.


It's been an El Nino season from Day 1.

During such seasons there is a greater chance of recurving storms out to sea because of developments occurring farther north, but there is also often a greater potential for developments close to land that end up making landfalls. This year has the pattern to favor in-close developments as well as those in the middle of the ocean that El Nino seasons are known for.
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Good morning all. There seems to be something brewing off of CA in the central Caribbean that is causing me concern. The satelitte images seem to indicate that the protective death ridge is moving which will allow a door into the GOM. I hope I am reading this incorrectly and encourage anyone on here to give me their opinion. Nothing we can do about it, but if a storm starts heading my way, I am going to the Grotto to pray for intervention.
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Great article, Aussie, thanks.
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Quoting sar2401:


Kman, you might be right, and I'll hop on board that train if TD7 starts to slow down. At 19 mph forward speed, both the shear and trades get magnified as potential problems for development.

How are you doing this morning, BTW?

me well fine tummy hurts from pasta and meat sause from last night but I'm still good
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Can you say SNOOZEFEST!!!
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hey levi. hows it going? good to see you and hope school is going well. are we already in an el nino season? or we are transitioning into one? it seems that even in the la nina years past couple of seasons, trade winds and dry air were a lot more than should have been. what do you make of that and what do you forsee higher chances of landfalling cyclones in the south versus storms going out to sea? thanks Levi. look forward to your insight. have a nice day.
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i am sure most everyone in here remembers hurricane frances back in 2004 which made landfall on the east coast of florida. The lat lon coordinates at which it started in the atlantic made it easier to cross westward and hit the CONUS. That and coupled with the atlantic high and less troughs. 93L has a good chance to go westward but chances of recurving at some point could be likely due to very few cv storms making it that far west at once. Nonetheless, it should be interesting to watch.
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Quoting ncstorm:
93L aint playing



Na it seems to be battling itself today ..but its pressure is good


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Quoting wunderkidcayman:

shear nah I say its either the same or maybe a little less but I'm leaning more on the same the ULL in the NW caribbean is lifting off to the NW taking the UL trough too so I am expecting lower shear than what most people think

personaly I think TD7 will pull some surprises on people because people are underestimating it alot yes it has dry air yes it has shear to deal with yes the trades are blowing abit but I think that people are "bigging up" this factors too much


Kman, you might be right, and I'll hop on board that train if TD7 starts to slow down. At 19 mph forward speed, both the shear and trades get magnified as potential problems for development.

How are you doing this morning, BTW?
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Thank you Dr. Masters
Member Since: October 3, 2008 Posts: 0 Comments: 6000
Good morning.

Blog update:

Tropical Tidbit for Friday, August 10th, with Video
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Quoting Bobbyweather:

Is the low level the thermosphere and the mid level the troposphere?


Troposphere 0-10km or 10,000mtrs or 34,000ft

1000 millibars (mb) = 100 kiloPascals (kPa) = 14.50 pounds per square inch (psi) and 29.53 inches of mercury. This works out to about 99% of the average air pressure at sea level.

Pressure drops off with elevation. The inverse altitude - atmospheric pressure relation can be seen in the requisite levels which have these approximate heights above sea level (ASL):

1000 mb ~ 360 feet (110 m)
850 mb ~ 5000 feet (1500 m)

700 mb ~ 10,000 feet (3000 m)

500 mb ~ 18,000 feet (5400 m)

250 mb ~ 34,000 feet (10,200 m)
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Quoting ncstorm:
anyone know how long it will take for the HH to get there??..are they taking off from the CONUS or one of the Lesser Antilles Islands?

They have to take off from the Lesser antilles or they will run out of gas
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Quoting AussieStorm:


Is this it??


Very interesting article.
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When will El Nino kick in. Next several weeks are the witching hours.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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