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 Neapolitan:

You have to get out more if you want to see the heavy weather. ;-) I do move around a lot: born in California; Iowa; Missouri; Alabama; back to California; Wyoming; Montana; back to Wyoming; Minnesota; Florida; Texas; Ohio; back to Florida; Colorado; back to Florida, back to California; back to Florida; back to California; and, now, back to Florida. Whew... ;-)


Dang man. You've been all over the place. Or at least all over the United States.

Anyway, I think I'll take your advice about getting out more and get my butt off the ol' seat in front of the monitor. I was just gonna stop by for a little, turned out to be in front of the computer for the last three hours lol

Out for now, see you all later tonight
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Just saw the 18Z GFS run..next run will be bermuda again..

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Quoting aquak9:

well...I figure every human deserves to hear happy birthday.


Ehhh, not every human.
Member Since: July 15, 2006 Posts: 17 Comments: 10156
Quoting angiest:


Must be using Dead Rat or S*cksy.


I've experimented with Red Hat, Fedora, Ubuntu, SUSE, Gentoo and Debian... they all have their pros and cons.
Member Since: August 19, 2008 Posts: 0 Comments: 825
Quoting Levi32:


All of the above and more with Linux :P


I never mentioned everything else though with a Mac, but if I wrote it down, it'd take up almost half the page here haha
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Quoting angiest:



Wubi would be a fit, it sounds like.


Yup. Wubi gives you no risk of destroying your Windows, as Ubuntu gets run within the Windows file system.
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Quoting robj144:


Linux is free, but it is not for the faint hearted.
Guess it's not for me then

Quoting Levi32:


It is free. There are multitudes of distributions, some requiring more advanced knowledge than others. Rob is right that it is not for the faint of heart, but the most popular distribution, Ubuntu, is very user-friendly and is basically the "Windows" of linux. It is aimed at beginners and requires little hands-on maintenance. For the most part, it takes care of itself, though you can still run into problems, just like Windows.


hmm. Well, maybe in the future I'll try and get a computer with Linux already on it. Like I said, I'm not very computer savvy. I can manage getting around the internet pretty well, but as far as the computer itself, and all the software, I don't know much. For now, I'll just stick with Windows. That scrolling method on the tabs is actually good enough for me.

Although, if I do ever get a desktop/laptop with Linux already on it, I'll be sure to come running asking for the script lol
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Quoting robj144:


Linux can be a real pain though sometimes. I manage our Linux network in my department, and some really strange problems crop up all the time that take days to fix.


This is true, especially if you are an experimental critter, but I have managed to get my distribution pretty rock-solid stable. If you're not playing with new kernels, servers, or massive clusters it's not too hard to keep it tame.
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Quoting MississippiWx:


I was going with the no one cares theme.

well...I figure every human deserves to hear happy birthday.
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Quoting robj144:


Linux can be a real pain though sometimes. I manage our Linux network in my department, and some really strange problems crop up all the time that take days to fix.


Must be using Dead Rat or S*cksy.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting Levi32:


All of the above and more with Linux :P


Linux can be a real pain though sometimes. I manage our Linux network in my department, and some really strange problems crop up all the time that take days to fix.
Member Since: August 19, 2008 Posts: 0 Comments: 825
Quoting JFV2013:
Mr. Cowan, I believe that Mr. EXAGGERATION has finally called into Bob's show.

no he hasn't yet. will be soon.
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Quoting aquak9:


it's legit. Happy birthday, JFV. Maybe you'll win the giveaway tonite.


I was going with the no one cares theme.
Member Since: July 15, 2006 Posts: 17 Comments: 10156
Quoting Levi32:


It is free. There are multitudes of distributions, some requiring more advanced knowledge than others. Rob is right that it is not for the faint of heart, but the most popular distribution, Ubuntu, is very user-friendly and is basically the "Windows" of linux. It is aimed at beginners and requires little hands-on maintenance. For the most part, it takes care of itself, though you can still run into problems, just like Windows.



Wubi would be a fit, it sounds like.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting JFV2013:
Guys, today is my birthday, does no one care? =(/


it's legit. Happy birthday, JFV. Maybe you'll win the giveaway tonite.
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Quoting nrtiwlnvragn:
770. TomTaylor

Easier to use Link
Yea, I've been to that link before. Same images, only problem is it's 3hr interval imagery, not 15 minute
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Quoting TomTaylor:
Is there a free download?

Don't think my parents would be willing to pay for something I already have and neither am I lol.

And if it is free, does it take much computer knowledge/awareness to install and operate and all that jazz? I'm not all that computer savvy.


It is free. There are multitudes of distributions, some requiring more advanced knowledge than others. Rob is right that it is not for the faint of heart, but the most popular distribution, Ubuntu, is very user-friendly and is basically the "Windows" of linux. It is aimed at beginners and requires little hands-on maintenance. For the most part, it takes care of itself, though you can still run into problems, just like Windows.
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Quoting HOTWHEELS99:
just watched our local weather here in florida at 8:15pm and bother stations just said 92 and 93 shouldnt be any concern along the east coastbetween the dry air all over and wind shear and the strong bermuda high if they even get going they will most likely follow the high and go out to sea and also they said theres at least 2 fronts comming down from canada that will push off the east coast next thursday and saturday that would block anything from the coast

take a breath !!!
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Quoting AussieStorm:
The Barometer Bob Show this week August 11, 2011. My guest is going to be Joe Bastardi from WeatherBell.Com. We will discuss the 2011 Hurricane Season. Are we in trouble?
Rob from RainmanWeather.Com will have another giveaway. Whats happening in the Tropics, and more. .
We will be talking Tropics and our Weather 101 segment!

The Barometer Bob Show is on now. You can watch the show via my blog also.

I'm a weather widow...
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The ensembles are becoming restless...

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Quoting caneswatch:


A Mac is the best. No viruses, no problems with the blog, no crashes. It's a great fit :)


All of the above and more with Linux :P
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Quoting TomTaylor:
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

You have to get out more if you want to see the heavy weather. ;-) I do move around a lot: born in California; Iowa; Missouri; Alabama; back to California; Wyoming; Montana; back to Wyoming; Minnesota; Florida; Texas; Ohio; back to Florida; Colorado; back to Florida, back to California; back to Florida; back to California; and, now, back to Florida. Whew... ;-)
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Quoting Levi32:


You should get it. You can run it alongside Windows and boot into either of them from a list at startup. Linux is what the cool guys use ;)


lol.
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no
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Quoting sunlinepr:


93L is un-argumentatively better organized than Invest 92L at this time.
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Quoting TomTaylor:
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


Roll he mouse wheel over the tab bar, more than likely that will cycle the tabs.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting JFV2013:
Guys, today is my birthday, does no one care? =(/



NO
Member Since: May 21, 2006 Posts: 5089 Comments: 114072
778. MTWX
Quoting USAFwxguy:


Thank you. Are you really in ID, and on a tropics forum?

Mt Home AFB.... like the nearby mountains. The national forest there are great.

Where else have you been stationed?
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770. TomTaylor

Easier to use Link
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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.
That's how we do it down here too. Take them off the smallest windows.
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775. GoWVU
Quoting USAFwxguy:
Shades of Hugo... landfall wise.



I sure hope not I was in Charleston that night in September 1989, NEVER want to go through it again!!
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Quoting Levi32:


You should get it. You can run it alongside Windows and boot into either of them from a list at startup. Linux is what the cool guys use ;)


A Mac is the best. No viruses, no problems with the blog, no crashes. It's a great fit :)
Member Since: Posts: Comments:
The Barometer Bob Show this week August 11, 2011. My guest is going to be Joe Bastardi from WeatherBell.Com. We will discuss the 2011 Hurricane Season. Are we in trouble?
Rob from RainmanWeather.Com will have another giveaway. Whats happening in the Tropics, and more. .
We will be talking Tropics and our Weather 101 segment!

The Barometer Bob Show is on now. You can watch the show via my blog also.
Member Since: Posts: Comments:
Quoting TomTaylor:
Is there a free download?

Don't think my parents would be willing to pay for something I already have and neither am I lol.

And if it is free, does it take much computer knowledge/awareness to install and operate and all that jazz? I'm not all that computer savvy.


Linux is free, but it is not for the faint hearted.
Member Since: August 19, 2008 Posts: 0 Comments: 825
Quoting TomTaylor:

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


To everyone else, who may not have been aware about what Levi and I are talking about:

There is great (~15 minute) satellite imagery over Africa available here. Only problem is it is a link to thousands of individual images, and it isn't an animation. There are a few ways around this, one way is to make the animation for yourself and another is to make a script. Problem with the first solution is it takes forever, and the problem with the second is you have to know what you are doing to make a script.

Another solution is to open up FireFox (idk if it works in other browsers, only checked Chrome and FF) and go to the link. Open up all the images you want in a new tab. Then hit the tab button on your keyboard once. You can now scroll through the images with your arrow key, effectively creating an animation. You get to control the speed and direction (forward/backward) of the loop. Only problem is you can't share it with other people.
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769. beell
12Z 200mb @ 264 hrs

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Quoting NCHurricane2009

Well IMO (in my opinion) 92L looks like trash right now...but if they were to go into Fujiwhara interaction, they would rotate counter-clockwise about each other....that would mean a more west track for 92L are a more NW track for 93L....

Thanks for the info.
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GFDL sped up forward speed




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13N/37.8W center of 92LLink
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Quoting Levi32:


You should get it. You can run it alongside Windows and boot into either of them from a list at startup. Linux is what the cool guys use ;)
Is there a free download?

Don't think my parents would be willing to pay for something I already have and neither am I lol.

And if it is free, does it take much computer knowledge/awareness to install and operate and all that jazz? I'm not all that computer savvy.
Member Since: Posts: Comments:
Member Since: August 2, 2010 Posts: 21 Comments: 9656
Quoting TomTaylor:
Well that's a real bummer lol


You should get it. You can run it alongside Windows and boot into either of them from a list at startup. Linux is what the cool guys use ;)
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Quoting 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



The ensemble mean of the same run for the same time makes a little more sense, though of course probably more smoothed out than it would be in reality due to the averaging of the members.

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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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