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 Levi32:


Linux is an entirely different operating system for the computer. In other words, it replaces Windows.
Well that's a real bummer lol

One thing I can do is open up all the tabs for the images and then click through all the tabs. That's the quick and easy way to get the animation. Only problem is I can't share it
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Quoting nrtiwlnvragn:


When I used to use boards once they went up, they were up for the season. Maybe take off 1 or 2 to let some light in the house.
Yep. Too much of a pain to deal with all that plywood...or all those golf cart roofs. :)
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Quoting cat6band:
Levi.....any chance at all that you see either one of these two getting into the GOM?? It's a hottub and I don't wanna think what may happen if something tries to move that way!!


The current pattern, as long as the ridge stays over Texas, tends to prevent things from getting into the Gulf of Mexico from the east, as the ridge blocks them, plus the weakness along the eastern seaboard likes to grab the storms and take them north before reaching the GOM. I wouldn't worry too much with 92L and 93L, but something developing farther west and getting into the western Caribbean would be more of a potential concern for the gulf. We may get some of those later this season.
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Quoting aquak9:

The house survived, it was like a cave inside though...cause they didn't get taken down for almost three months! Sure made us all laugh.


When I used to use boards once they went up, they were up for the season. Maybe take off 1 or 2 to let some light in the house.
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Quoting floodzonenc:
Does that thang come with a turbocharger?



It's turbo'd up all by itself :P
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Levi.....any chance at all that you see either one of these two getting into the GOM?? It's a hottub and I don't wanna think what may happen if something tries to move that way!!
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752. beell
This post is a little late I guess. The jet stream on the 18Z GFS at 264 hrs is quite different from the 3 previous runs.

Not to say it could not happen, but that is the longest, straightest upper jet segment I have seen (or remember anyway). Especially for August. 100 knot jetstreak. Nary a dip or a turn from out in the NW Pacific almost all the way across North America. This probably would quickly take the kink out of any east coast/western ATL troughing. Looks a little hokey.

93L's strong outflow can be seen in the closed isohype over FL and the Bahamas.

18Z 200mb @ 264 hrs
click to enlarge

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Quoting USAFwxguy:


Didn't that shatter the windows?

J/K... that is being resourceful!

The house survived, it was like a cave inside though...cause they didn't get taken down for almost three months! Sure made us all laugh.
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I forgot where I read it but a met said that this year looks like 2004. All I could say to myself was this guy's a idiot.
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Quoting Levi32:


No. I have heard of such things as Firefox scripts, but I have no idea what they are, and I don't run scripts within the browser. They are invoked from a shell.
I thought you said something like "I can give you the scripts to make the GIF if you ever want them." But I'm pretty sure you said something like they were for Linux or run on Linux?

Idk I'm lost

Quoting Levi32:


Linux is an entirely different operating system for the computer. In other words, it replaces Windows.
ooh.

That explains it.
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Five minutes ago - "Jeopardy!" College Championship:

Trebek: Hans from Florida, what is your dream job?
Hans: Hurricane Hunter!




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Quoting TomTaylor:
you said something about the script being specific to some web browser that I'm pretty sure I don't have. I have IE, FF, and Chrome.

Or I thought you said something like that. Wasn't it Linux?


Linux is an entirely different operating system for the computer. In other words, it replaces Windows.
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Quoting TomTaylor:
you said something about the script being specific to some web browser that I'm pretty sure I don't have. I have IE, FF, and Chrome.

Or I thought you did.


No. I have heard of such things as Firefox scripts, but I have no idea what they are, and I don't run scripts within the browser. They are invoked from a shell.
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742. JLPR2

Loop

92L lost its round shape, needs to do some remodeling to get going. XD
Member Since: September 4, 2007 Posts: 7 Comments: 8653
Quoting Levi32:


What? Web browser? When I have command-line? I wrote a BASH script for it that invokes "curl" to download files, and imagemagick to create GIF animations with the data that is downloaded.
you said something about the script being specific to some web browser that I'm pretty sure I don't have. I have IE, FF, and Chrome.

Or I thought you said something like that. Wasn't it Linux?
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On boarding up windows- Had a friend, ran a golf cart repair business outta his garage. In '04, they never had to board up- he just nailed golf cart roofs over all the windows.
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Quoting MississippiWx:


Don't talk about Grothar that way...

Just because he's old and can't walk very well doesn't mean he's a GIMP.
It's a pic editing program lol
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Quoting TomTaylor:
oh. my. god.

What is the name of the web browser you use for this?


What? Web browser? When I have command-line? I wrote a BASH script for it that invokes "curl" to download files, and imagemagick to create GIF animations with the data that is downloaded.
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Quoting Neapolitan:

For the hailstorm, I lived in Huntington Beach about two miles from the water. For the rain, I was in Ventura County about four miles from the ocean as the crow flies. (That was the same rain event that cause the mudslide at La Conchita that killed 10 people; I lived on the other side of the hill from there.)

I also remember the remnants of a tropical storm or hurricane that made their way into Orange County; it was the first time I'd ever seen windblown rain. ;-)
Ah gotcha. I've lived in coastal San Diego (near Clairemont and La Jolla to be more specific) all my life, so I've seen mild weather just about all my life.

At my house...

I've never seen the temp gauge drop below 25F, or above 105. Never seen hail larger than half an inch. Never seen it snow. Never seen it rain more than 2.5 inches in a day. Never seen thunderstorms (over my house...it's pretty common to see them in the distance) for more than one day in a row.

Pretty mild weather.



Also sounds like you move around a lot man
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Quoting PlazaRed:
Noting:- 677. Levi32
I'm a bit late with the comment on this one from Levi but it seems to me that this line of storms and general activity over Africa is a long way north, it appears to be going over the southern Sahara desert.
My thoughts are, are these storms that Neo called the African train the other night going to move even further north as the season progresses?


They are just about as far north as they usually get during the peak of the season. They usually won't venture farther north than that. We're entering the maximum strength of the African wave season.
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Quoting BahaHurican:
Hey, aqua. We still getting some wild runs from the various models here..... did u get rain today? I thought I read something about rain in N FL...


It was a nostalgic piece.

Yeah the model runs are bonkers. Real sweet that Levi saved that one, it's classic.

Put me in the cone 12 hours out, and then we'll talk. :)
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Quoting aquak9:

take a breath!!
Hey, aqua. We still getting some wild runs from the various models here..... did u get rain today? I thought I read something about rain in N FL...
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92L still has a long way to go before it's anything close to a tropical cyclone. 93L still has the better chance for now.

92L

Member Since: July 15, 2006 Posts: 17 Comments: 10200
Noting:- 677. Levi32
I'm a bit late with the comment on this one from Levi but it seems to me that this line of storms and general activity over Africa is a long way north, it appears to be going over the southern Sahara desert.
My thoughts are, are these storms that Neo called the African train the other night going to move even further north as the season progresses?
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Quoting weatherh98:


A b f



Sorry read wrong abf
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Beven likes those crayons!
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Little purple in the SW Caribbean again.
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Quoting Levi32:


~10 seconds, perhaps longer if the files are large and numerous.
oh. my. god.

What is the name of the web browser you use for this?
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Quoting angiest:


it never ceases to amaze, or amuse, me the number of people who live on the coast and still have to rush out at the lst minute for plywood and the like.
Only thing is, it's not really funny. More like ironic.

But we see a whole lot of that here, too. A lot of times the plywood is just discarded afterwards.... and it's EXPENSIVE. U talking $25 / sheet for one-sided.... Pple putting tape Xes on their windows and praying for God to save them.... Sheesh.

I say, let pple play with the possibilities 13 days out. The reality is, every one of those runs is a POSSIBLE storm track... may not happen this time or the next, but maybe somebody out there who's thinking "it can't happen to NC/SC/GA/FL" and so on might get "scared serious".....
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ITS POSTED AGAIN
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Quoting aquak9:

take a breath!!


Good grief, beating yourself up kid.
Member Since: September 2, 2006 Posts: 110 Comments: 6876
Quoting TomTaylor:


I guess I should be a little more specific-whether along coastal Southern California can be pretty boring. If you go inland a little, the marine layer becomes much less of an issue. You also get much more rain during the winter's and a better chance of some monsoonal action coming off the mountains to the East. Right along the coast, the marine layer is here just about everyday by nighttime. Only exception is when we get really strong ridging in our area or just to the east like we see during Santa Ana events.

Sounds like you must have lived a little ways away from the coast in some higher elevation if you got that kind of hail and rain during one rain event. I remember 2005 as well, we got about 21 or 22 inches of rain at my house for the entire season, not one rain event lol. Still was more than double our average, so it was neat getting all the rain and seeing everything so green.

For the hailstorm, I lived in Huntington Beach about two miles from the water. For the rain, I was in Ventura County about four miles from the ocean as the crow flies. (That was the same rain event that cause the mudslide at La Conchita that killed 10 people; I lived on the other side of the hill from there.)

I also remember the remnants of a tropical storm or hurricane that made their way into Orange County; it was the first time I'd ever seen windblown rain. ;-)
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Guys the TWO was already posted.

40% on both 92L and 93L
10% Florida AOI.
Member Since: September 2, 2006 Posts: 110 Comments: 6876
Quoting weatherh98:


Doesn't it though and think about all of the fatalities that occur from no pre season prep, honestly I think 93 l will beat 92 l to development because it doesn't have to fight the dry air as much as 92 l does simply from 92 l moistening the atmosphere up and also because 93 l has been sustaining it's thunderstorms and 93 l has been going through diurnal min and max much less than 92 l

take a breath!!
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ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT THU AUG 11 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

1. A BROAD AREA OF LOW PRESSURE CENTERED ABOUT 850 MILES WEST OF
THE SOUTHERN CAPE VERDE ISLANDS IS MOVING WESTWARD AT 10 TO 15 MPH.
THE ASSOCIATED SHOWER AND THUNDERSTORM ACTIVITY HAS BECOME A LITTLE
LESS ORGANIZED DURING THE LAST 24 HOURS. HOWEVER...ENVIRONMENTAL
CONDITIONS APPEAR FAVORABLE FOR GRADUAL DEVELOPMENT OVER THE NEXT
SEVERAL DAYS. THIS SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

2. A LOW PRESSURE SYSTEM LOCATED ABOUT 225 MILES SOUTH OF THE SOUTHERN
CAPE VERDE ISLANDS IS PRODUCING A LARGE AREA OF CLOUDINESS AND
SCATTERED THUNDERSTORMS. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO
GRADUALLY BECOME MORE CONDUCIVE FOR DEVELOPMENT OVER THE NEXT
SEVERAL DAYS AS IT MOVES WESTWARD AT 15 TO 20 MPH. THIS SYSTEM HAS
A MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.

3. DISORGANIZED SHOWERS AND A FEW THUNDERSTORMS LOCATED OVER THE
ATLANTIC ABOUT MIDWAY BETWEEN THE CAROLINAS AND BERMUDA ARE
ASSOCIATED WITH A BROAD TROUGH OF LOW PRESSURE. DEVELOPMENT...IF
ANY...SHOULD BE SLOW TO OCCUR AS THE TROUGH MOVES NORTHEASTWARD AT
15 TO 20 MPH. THIS SYSTEM HAS A LOW CHANCE...10 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN
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716. JLPR2
Quoting JrWeathermanFL:
Poll time!



What will 93L be at 8:00?
A.40%
What will 92L be at 8:00?
F.Less
What will the AOI off the East Coast be at 8:00?
A.10%
Member Since: September 4, 2007 Posts: 7 Comments: 8653
Quoting JrWeathermanFL:
Poll time!
What will 93L be at 8:00?
A.40%
B.50%
C.60%
D.70%
E.More
F.Less

What will 92L be at 8:00?
A.40%
B.50%
C.60%
D.70%
E.More











Baf




F.Less

What will the AOI off the East Coast be at 8:00?
A.10%
B.20%
C.30%
D.40%
E.More
F.Less



A b f
Member Since: Posts: Comments:
Quoting angiest:


it never ceases to amaze, or amuse, me the number of people who live on the coast and still have to rush out at the lst minute for plywood and the like.


Doesn't it though and think about all of the fatalities that occur from no pre season prep, honestly I think 93 l will beat 92 l to development because it doesn't have to fight the dry air as much as 92 l does simply from 92 l moistening the atmosphere up and also because 93 l has been sustaining it's thunderstorms and 93 l has been going through diurnal min and max much less than 92 l
Member Since: Posts: Comments:
TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT THU AUG 11 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD AREA OF LOW PRESSURE CENTERED ABOUT 850 MILES WEST OF
THE SOUTHERN CAPE VERDE ISLANDS IS MOVING WESTWARD AT 10 TO 15 MPH.
THE ASSOCIATED SHOWER AND THUNDERSTORM ACTIVITY HAS BECOME A LITTLE
LESS ORGANIZED DURING THE LAST 24 HOURS. HOWEVER...ENVIRONMENTAL
CONDITIONS APPEAR FAVORABLE FOR GRADUAL DEVELOPMENT OVER THE NEXT
SEVERAL DAYS. THIS SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

A LOW PRESSURE SYSTEM LOCATED ABOUT 225 MILES SOUTH OF THE SOUTHERN
CAPE VERDE ISLANDS IS PRODUCING A LARGE AREA OF CLOUDINESS AND
SCATTERED THUNDERSTORMS. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO
GRADUALLY BECOME MORE CONDUCIVE FOR DEVELOPMENT OVER THE NEXT
SEVERAL DAYS AS IT MOVES WESTWARD AT 15 TO 20 MPH. THIS SYSTEM HAS
A MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.

DISORGANIZED SHOWERS AND A FEW THUNDERSTORMS LOCATED OVER THE
ATLANTIC ABOUT MIDWAY BETWEEN THE CAROLINAS AND BERMUDA ARE
ASSOCIATED WITH A BROAD TROUGH OF LOW PRESSURE. DEVELOPMENT...IF
ANY...SHOULD BE SLOW TO OCCUR AS THE TROUGH MOVES NORTHEASTWARD AT
15 TO 20 MPH. THIS SYSTEM HAS A LOW CHANCE...10 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
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Quoting JrWeathermanFL:
Poll time!
What will 93L be at 8:00?
A.40%
B.50%
C.60%
D.70%
E.More
F.Less

What will 92L be at 8:00?
A.40%
B.50%
C.60%
D.70%
E.More
F.Less

What will the AOI off the East Coast be at 8:00?
A.10%
B.20%
C.30%
D.40%
E.More
F.Less



B A A
Member Since: September 2, 2006 Posts: 110 Comments: 6876
40/40/10 again
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Quoting MississippiWx:
All of the salivating over where the GFS sends 93L in 300+ hours is a little ridiculous. It's no surprise that one run shows landfall, the next out to sea since it's so far out in the run.

We should be more worried about development of the actual system first, then trying to see if the models can lock down on a particular upper level pattern for steering. For now, they are going to take complete 180 degree turns each run.
Hey, we r just having fun with it for now.... lol ... while waiting slowly....
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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.