Two African waves, 92L and 93L, worth watching

By: Dr. Jeff Masters , 2:59 PM GMT on August 11, 2011

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An African wave is near 13°N 35°W, about 700 miles west-southwest of the Cape Verde Islands. This system, (Invest 92L), is moving west to west-northwest at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands early next week. Recent visible satellite loops show that 92L has less heavy thunderstorm activity near where it is trying to develop its circulation center than yesterday. Water vapor satellite loops that a large area of dry air lies just to the west of 92L, but the atmosphere in the immediate vicinity of 92L is moist. Even so, the decline of heavy thunderstorm activity since yesterday implies that dry air is probably working its way into 92L. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 15 knots affecting 92L. Sea surface temperatures are 26.5° - 27°C, which is very close to the 26.5°C threshold usually needed to support a tropical storm.


Figure 1. Morning satellite photo of Invest 92L and Invest 93L.

Forecast for 92L
Low to moderate wind shear of 5 - 15 knots is predicted along 92L's path over the coming three days, which should allow the storm to organize, assuming it can shut out any incursions of dry air that might intrude. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET) show weak development or no development of 92L, and NHC gave 92L a 30% chance of developing into a tropical depression by Saturday morning in their 8am outlook. A steady west to west-northwest motion for 92L is predicted by all of the models, which would put the storm in the vicinity of the northern Lesser Antilles Islands by Sunday. On Saturday and Sunday, 92L is expected to enter a region where an upper-level low pressure system will bring high wind shear of 20 knots to the storm, which should slow development. This upper-level low is also expected to turn 92L more to the northwest, so the storm is likely to pass north of the Lesser Antilles, though may pass close enough to give heavy rains to the northernmost islands. It is too early to know if 92L will recurve out to sea and potentially threaten Bermuda, or continue to the northwest towards the U.S. East Coast.

93L
An African wave that emerged off the coast of Africa is near 10°N 22°W, a few hundred miles south of the Cape Verde Islands. This system, (Invest 93L), is also moving west at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands near the middle of next week. Recent visible satellite loops show that 93L has a decent amount of heavy thunderstorms, but this activity is not well organized. There is not much spin associated with 93L yet. 93L is fairly well-protected from dry air to its north and west. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 20 knots affecting 93L. Sea surface temperatures are 27.5°C, which is one degree above the 26.5°C threshold usually needed to support a tropical storm.

Forecast for 93L
Moderate wind shear below 20 knots is predicted along 93L's path over the coming five days, which should allow the storm to steadily organize. 93L is about 600 miles east of 92L, which is close enough that the two systems may interfere with each others' organization. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET), have only one model, the GFS, that is indicating significant development of 93L. This model brings 93L near the northern Lesser Antilles Islands by Wednesday. NHC gave 93L a 20% chance of developing into a tropical depression by Saturday morning in their 8am outlook. Due to moister air, the potential for less wind shear, and a more southerly track, 93L is probably a greater threat to the Lesser Antilles than 92L.

Jeff Masters

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Quoting EYEStoSEA:


You're so right....ya get a little rain and then you pay for with the sultry steam....but glad you did get a little reprive...:)
me too, hoping this reprieve equates to that evil high pressure going on vacation somewhere else for a while.
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92L's slow development may allow it to get farther westward before any type of re-curvature.
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456. srada
?
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455. JRRP

93L
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Quoting NavarreMark:


Don't know why, but when I see your posts I always have a visual of Barney Frank for some reason.


I know why when you post I always have a visual of this guy:



:^P
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Quoting AegirsGal:
Yup, got a little bit where I am, the front felt great coming through and after the rain we were down to mid 80s. Temp creeping back up and all the rain has since evaporated.


You're so right....ya get a little rain and then you pay for with the sultry steam....but glad you did get a little reprive...:)
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Quoting weaverwxman:
that was quite the model run a lil scary and at the same time puzzling as to how that could happen but storns have made loops and come back to bite us Cleo did


if you are referring to the link i posted, that wasn't so much of a loop de loop as a slam on the brakes and put it in reverse while the second storm waits for the first to finish backing up before it puts it into drive again...that would be a slam for at least 5 states at one time...and at least GA, SC, and NC would get whammied 3 times each
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Quoting USAFwxguy:


Oh I see. I noticed the Ignore User link. Now I know why that is there, I guess.
Yeah. The blog's supposed to be mostly self-moderated, which has its good and bad points. We've gotten better at keeping the troll-related noise down. Mainly just ignore or flag the obvious baiters and troublemakers and u should be ok.... And as others have said, we have some very good bloggers on here... and an excellent shift system so whether u r on at 5 a.m., or 11 a.m. or their p.m. versions, there's usually some reasonable conversation to be had.

Also have to give a shout out to the Caribbean and islands contingent in here, which IMO is one of the best things about this blog. Gives on the ground information that is otherwise not generally available on the net.... and we are cute, too! lol Actually we are pretty eclectic in here; I think we lack African bloggers, but other than that we've got a pretty extensive global community for a little blog from Michigan....
Member Since: October 25, 2005 Posts: 19 Comments: 21187
Quoting cloudburst2011:



omg the shit is starting to get deep in here...


Remember that list of good sources that was posted earlier?

Notice that cloudburst2011 wasn't on it?

'nuff said...
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Quoting EYEStoSEA:
Yup, got a little bit where I am, the front felt great coming through and after the rain we were down to mid 80s. Temp creeping back up and all the rain has since evaporated.
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Quoting MTWX:

Now if only that entire system was traveling across Texas instead of OK! (I know OK could use that rain too though)


Exactly...if I could conjole it down there...I would !
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Quoting weaverwxman:
that was quite the model run a lil scary and at the same time puzzling as to how that could happen but storns have made loops and come back to bite us Cleo did

If memory serves me correct didnt hurricane Jeanne loop around before striking Florida. Btw first post! Been lurking for years. You all do a great job
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441. JLPR2
Quoting pottery:

Nothing calling for anything strong, so far.
But watch out for the Rain-Rates.....


That's the worst part of it, rivers here would overflow easily if an Emily-like rain event occurs.
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440. MTWX
Quoting EYEStoSEA:

Now if only that entire system was traveling across Texas instead of OK! (I know OK could use that rain too though)
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Quoting K8eCane:



Why do I think of ABBA when you post?


It ain't cause I'm a dancing queen, though I do look good in a pair of heels.

And I'm not a ABBA fan, though in certain situations they are appropriate.

My voice could make a dying wildebeast sound like a symphony.

IDK......you tell me.
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Quoting PaulinJax:



I cetainly hope that is one of those models that is never right... I live in N FL


it is HIGHLY UNLIKELY that would pan out...
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Quoting JLPR2:


Yep, EURO says close call. Models are trending south and west.

Nothing calling for anything strong, so far.
But watch out for the Rain-Rates.....
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Quoting angiest:


No, it won't. He overwrites the images every 24 hours. If you pull it up tomorrow it will be different. Unfortunately, it looks like manually saving all of the images from http://raleighwx.americanwx.com/models/18zgfs.html for the 500mb Heights/PMSL Atlantic Tropical parameter is the only thing that will work, and that is exceptionally tedious.


crud...i for one do not have the time it would take nor the experience to do that...but i will say that it was BURNED into my memory forever lol...
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Quoting rv1pop:
Looking at your favorite location on the radar, what is your location? Morris-dido hwy?


Not far from there actually, I reside in the exclusive Vaquero Club off of in 114 Westlake, perhaps you've heard of it, Sean Peyton, Glen Beck and the Jonas Bros. are just a few of my neighbors.
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431. JLPR2
Quoting pottery:

Could make it anywhere, at this stage....
Initially the Caribbean needs to keep an eye on this one.
ESPECIALLY the Northern Islands.


Yep, EURO says close call. Models are trending south and west.
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Quoting tiggeriffic:
I think the wildest model posted was one i got to see yesterday or the day before...compliments of WU lol... really can't see that it could even happen at this point let alone ever but a model did come up with it...play it in super slow motion to get the full effect of 92 and 93 it is wicked wild...

Link



I cetainly hope that is one of those models that is never right... I live in N FL
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Quoting tiggeriffic:


i wonder since it is in my favorites as THAT particular model if it would keep it as such? really would like to hang onto that one lol


No, it won't. He overwrites the images every 24 hours. If you pull it up tomorrow it will be different. Unfortunately, it looks like manually saving all of the images from http://raleighwx.americanwx.com/models/18zgfs.html for the 500mb Heights/PMSL Atlantic Tropical parameter is the only thing that will work, and that is exceptionally tedious.
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Quoting Stormchaser2007:
It appears the 18z suite for 93L has shifted south. Could make it into the NE Caribbean.


Could make it anywhere, at this stage....
Initially the Caribbean needs to keep an eye on this one.
ESPECIALLY the Northern Islands.
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Quoting angiest:


Unfortunately, the only way I know of is to save every image in that run as a separate file. The loop is a java applet that takes all of the images for a given run of GFS and loops them together.

Unfortunately, he seems to have permissions set up such that wget can't go grab them all.


i wonder since it is in my favorites as THAT particular model if it would keep it as such? really would like to hang onto that one lol
Member Since: September 16, 2007 Posts: 0 Comments: 3650
It appears the GFS was correct in it's modeling of Invest 93L developing an area of strong vorticity in the heavy convective burst that formed yesterday.

There appears to be a very pronounced ML swirl despite 30 knots of easterly shear.
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424. MTWX
Quoting tiggeriffic:


it was fixed by the poster...it wasn't intentional, it was part of a quote thing and has been resolved, ty tho :)

I know it wasn't ( I forget sometimes too!) Just anoying when you are trying to read.
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Quoting weaverwxman:
jist hit the refresh page and it will go away tigger


that was 2 or 3 pages ago...thanks tho...it has been fixed for about 100 posts now... :)
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Quoting debrisball:

Not going to put a dent in the drought by any means, but when you've had over 40 consecutive 100 degree days (today's rain may have a chance to end the streak 2 days short of the record, we'll see) and over 2 months without a drop of rain it's pretty exciting to even see that coming on the radar.
Looking at your favorite location on the radar, what is your location? Morris-dido hwy?
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omg 93L may beat 92L and be come a TD 1st
Member Since: May 21, 2006 Posts: 5091 Comments: 114653
jist hit the refresh page and it will go away tigger
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Quoting tiggeriffic:


email me how to do it...i have it saved just like this in my favorites...i have a second tab open with it running now...tell me how to archive it and i will save it on my puter for later reference


Unfortunately, the only way I know of is to save every image in that run as a separate file. The loop is a java applet that takes all of the images for a given run of GFS and loops them together.

Unfortunately, he seems to have permissions set up such that wget can't go grab them all.
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Quoting MTWX:

Someone posted an unaltered Youtube video again! It streches the screen on mine too. Just got to wait for post 400 to turn the page over.


it was fixed by the poster...it wasn't intentional, it was part of a quote thing and has been resolved, ty tho :)
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Quoting ILwthrfan:


KEEPEROFTHEGATE
Pottery
AtmoAggie
Reedzone
Levi32
Hyrdrus
Collition
Grothar
Patrap
Neapolitian

These guys are great sources of INFO and do a great job breaking down things and know far more than I ever will. But To answer your question I believe that the gulf coast storm your referring to in the GFS output was from the tail end of a trough laying across Florida. The other was 92L I believe riding up the East coast, but I know the Gulf storm wasn't 93L. Any storm right now coming off Africa would have a VERY LOW chance making it all they west into the Gulf Of Mexico.


Thanks for the mention, I do my best to give out the reality of outcomes y looking at the patterns and steering and some models that trend toward what the pattern shows. I like the models on both invests today, it makes sense. A storm recurves west of Bermuda then the weakness closes and allows the other to head more towards the CONUS. A classic example was Edouard and Fran in 1996.
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93L needs to be watch it will be come a big storm may be 92L has well
Member Since: May 21, 2006 Posts: 5091 Comments: 114653
415. MTWX
Quoting tiggeriffic:
was lurking...initially my page was ok...now it is, well, a bit flukey...no avatars, weird looking...anyone else having the problem?

Someone posted an unaltered Youtube video again! It streches the screen on mine too. Just got to wait for post 400 to turn the page over.
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414. JLPR2
93L seems to be on its way to be a TD.

11/1745 UTC 11.2N 21.2W T1.0/1.0 93L -- Atlantic
Depending on how well it does tonight we might have a TD tomorrow, becoming our first CV storm.

On the other hand 92L...
11/1745 UTC 13.7N 35.1W TOO WEAK 92L
I don't see 92L developing soon, maybe once it gets to 54w and hits warmer waters.

Well now, anyone wants to tell me if I'm mistaken, I was out all day and that is what I got from looking at satellite images and vort maps.
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is KEEPEROFTHEGATE like and auto-igmore user, all his posts are gone for me, and i didnt ignore him?
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It appears the 18z suite for 93L has shifted south. Could make it into the NE Caribbean.

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264. Squid28 2:33 PM EDT on August 11, 2011

Bravo and well said.... u need to make this an entry in your own blog and repost it every August..... really captures what the dynamics of this blog is like....
Member Since: October 25, 2005 Posts: 19 Comments: 21187
Quoting kshipre1:
this maybe an elementary question for many of you but I am trying to learn more about fronts, pressure systems, etc...

As I understand, troughs could recurve storms but could the High pressure also?

I read somewhere that if storms get close enough to the clockwise ciruclation, the storms could go out to sea

also, what does the ridge over Texas have to do with landfalling cyclones on the east coast?

anyone? thanks


ok, i am not expert, but am good at the elementary level of explaining things cuz that is how I understand it too lol...the intensity of the storm is one factor of what stears it. The weaker the storm the less likelihood that a HIGH will control it. Tropical storms are low down...they build in height as they get stronger. A high is just that...high up... a high spins clockwise, if it is over the coastline and water, it will stear a storm into land, if it is over open water, it makes a path for the storm to follow over the water...there are a million other variables in there...but that is the best way i can explain it and the way it was explained to me several years ago when i joined
Member Since: September 16, 2007 Posts: 0 Comments: 3650
that was quite the model run a lil scary and at the same time puzzling as to how that could happen but storns have made loops and come back to bite us Cleo did
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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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