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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This is an example of how dry it is here in League City Texas:

7. All restaurants are prohibited from serving water to patrons except upon request of the patron
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Member Since: June 7, 2007 Posts: 4 Comments: 961
Quoting depstein:
I'm not that up on meteorology but I know some of you are. Do you think that if invests 92 and 93 develop, we could see the Fujiwara effect?
If not why?
If so, how might this affect the track?


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....
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Quoting Levi32:


If 92L doesn't accelerate as expected and the two start interacting, chances are 92L would be left standing at the end, as it is much larger, and not fully integrated into the ITCZ like 93L still is.


How can you tell if a system is integrated into the ITCZ versus not? Aren't tropical waves low pressure areas already seperate from the ITCZ at their inception?

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I'm not that up on meteorology but I know some of you are. Do you think that if invests 92 and 93 develop, we could see the Fujiwara effect?
If not why?
If so, how might this affect the track?
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93l looks better than 92L.
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Levi, has the cooling of the Gulf of Guinea having already an effect in what is going on in the Eastern Atlantic?

Member Since: April 29, 2009 Posts: 75 Comments: 14267
Quoting Levi32:
12z HWRF and GFDL actually don't develop 93L that much, possibly because of its tendency to re-integrate into the ITCZ, which could be an issue that prevents significant development. That's one thing to keep in mind is that development of these two invests is far from guaranteed, despite what the GFS says.
Weird that they take it to the ITCZ again.
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Heads up, the 18Z GFS is running:

Link
Member Since: August 12, 2007 Posts: 11 Comments: 2448
Quoting kmanislander:


Hi Levi,

Those models dont do too well until a system is classified, as you know. I wouldn't draw any conclusions about strength based upon early runs until we actually get something spun up and classified as a TD or above.


True, but regardless, I like to see the HWRF do it's usual thing with blowing up systems as bad as the CMC. If the WRF or HWRF doesn't make something feedback in the tropics, then I take that as a hint that there may be issues. Often, there are. We'll see. Both systems still have a decent shot. It is mid-August now, after all.
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Quoting Levi32:
12z HWRF and GFDL actually don't develop 93L that much, possibly because of its tendency to re-integrate into the ITCZ, which could be an issue that prevents significant development. That's one thing to keep in mind is that development of these two invests is far from guaranteed, despite what the GFS says.
Guess that's why NHC isn't going above 40% right now... that's still only a 4 in 10 chance either will do anything anytime soon....
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Quoting Stormridr911:
I was going to ask if it's possible that the stronger of 92 or 93 could possible pull the energy from and absorb the other a little earlier...however it appears that my already be happening. Chances of 93L over taking 92...pretty good?


If 92L doesn't accelerate as expected and the two start interacting, chances are 92L would be left standing at the end, as it is much larger, and not fully integrated into the ITCZ like 93L still is.
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Quoting Levi32:
12z HWRF and GFDL actually don't develop 93L that much, possibly because of its tendency to re-integrate into the ITCZ, which could be an issue that prevents significant development. That's one thing to keep in mind is that development of these two invests is far from guaranteed, despite what the GFS says.


Hi Levi,

Those models dont do too well until a system is classified, as you know. I wouldn't draw any conclusions about strength based upon early runs until we actually get something spun up and classified as a TD or above.
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Quoting KEEPEROFTHEGATE:
its where they normally seperate from the ITCZ and fire on there own if they got the jam it will be good to go


Never knew that! Learn something new here every day.
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I was going to ask if it's possible that the stronger of 92 or 93 could possible pull the energy from and absorb the other a little earlier...however it appears that my already be happening. Chances of 93L over taking 92...pretty good?
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Quoting flwthrfan:


hmmm, the local channels in south fl are saying it's far out there and we will need to keep an eye on it but nothing to worry about right now...
Pretty much SOP with Twaves E of 50W for them. No use getting all heated when the storm is 5 days from impacting any land whatsoever, and 7-10 days from any potential FL impact.....
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Quoting NCHurricane2009:


What is siginifcant about 30 to 45W?
It's where they r supposed to start detaching themselves from the monsoon trough.... can they spin up a good centre by then? Make it on their own?
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12z HWRF and GFDL actually don't develop 93L that much, possibly because of its tendency to re-integrate into the ITCZ, which could be an issue that prevents significant development. That's one thing to keep in mind is that development of these two invests is far from guaranteed, despite what the GFS says.
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Quoting NCHurricane2009:


What is siginifcant about 30 to 45W?
its where they normally seperate from the ITCZ and fire on there own if they got the jam it will be good to go
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537. beell
NOAA New Climate Normals
Quoting Levi32:
Here's some pretty big news for those of you who, like me, enjoy looking at patterns from the past. ESRL NCEP Reanalysis is changing the long-term climatology period from 1968-1996 to 1981-2010. This will make maps look different, sometimes quite a bit different, than they were before. I just figured this out when looking at the ridge orientation in one of my hurricane analog maps.


This change applies to a wide range of climate products. We are leaving a cooler 70's decade behind for a warmer 80's.

Some electric utilities base their rates on 30 year climate normals. They are glad to say goodby to the cool 70's. Warmer temps bring less revenue under the old 30 year normals.

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12Z the 17th August. The GFS has 92L recurving and 93L impacting the islands. The run finishes at 180 hrs with a strong system parked over PR.

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Quoting KEEPEROFTHEGATE:
!!! Was that a Canada hit I saw at the end of that run???
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Quoting HOTWHEELS99:
the local weather channels here in florida at 5pm are all saying that between the 3 fronts that comming down across the us next week and the bermuda high both 92 and 93 should recurve away from the east coast lets hope they are right


hmmm, the local channels in south fl are saying it's far out there and we will need to keep an eye on it but nothing to worry about right now...
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533. JLPR2
Quoting NCHurricane2009:


Not surprised, 92L looks fairly sloppy right now in satellite pics....


Might try something further down the road but I'm thinking that 40% from the NHC should go down in the next update.
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Quoting BahaHurican:
Sun just went down about where 92L and 93L are... this bit between 30 and 45W is where we see if they fizzle or make it.


What is siginifcant about 30 to 45W?
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Sun just went down about where 92L and 93L are... this bit between 30 and 45W is where we see if they fizzle or make it.
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so if 92L fades a way then it looks like 93L will be are big boy then
Member Since: May 21, 2006 Posts: 5091 Comments: 115125
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527. srada
Quoting tropicfreak:


I wasn't talking about any trolls.


"they" wont tell you they minus your post. I bet if this was like facebook where it shows who minus and plus someone's post then you wouldn't even be hidden right now. If it makes you feel better, I dont plus or minus anyone's post and I could care less who minus or plus mine. My self esteem is high enough to where I dont need affirmation if someone likes my post or not The only option that should be used on posting is reporting someone.
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Tfreak, mail.
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Quoting JLPR2:
92L's 850mb vort is fading away.



Not surprised, 92L looks fairly sloppy right now in satellite pics....
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Thanks, Levi32. I truly appreciate all your work here. I have been here for a few years but was afraid to comment until I got involved with Free to Air satellite reception, and I understand TV and electronics. Been posting there for quite a while and also teaching some "living off grid" lessons so now I can talk with my fingers - usually way too much!
Thank again for teaching me about the weather.
POP
Member Since: August 18, 2007 Posts: 0 Comments: 191
523. JLPR2
92L's 850mb vort is fading away.

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Quoting HOTWHEELS99:
the local weather channels here in florida at 5pm are all saying that between the 3 fronts that comming down across the us next week and the bermuda high both 92 and 93 should recurve away from the east coast lets hope they are right


the only problem with that forecast is that 92 and 93 are WAY more than just a week away...what happens next week can change by the time 92 and 93 make it this far
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Looks like 92L and 93L are slowly breaking away from the ITCZ...Let's see what they can do over the next 48hrs
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Quoting BahaHurican:
Relax... random attrition. It's happened to a few of us lately. BTW, I do suggest u stop talking to and about those trolls... that WILL cause pple to [-] and [!] ur posts...



I wasn't talking about any trolls.
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Quoting HOTWHEELS99:
the local weather channels here in florida at 5pm are all saying that between the 3 fronts that comming down across the us next week and the bermuda high both 92 and 93 should recurve away from the east coast lets hope they are right


Are you sure?
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92L looks really messy, I am suprised it has a 40% chance right now in the Atlantic TWO
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Quoting tropicfreak:
Am I on anyone's ignore list? Post 402 didn't deserve to be removed.


not mine
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93 is a west mover
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Hotwheels99 - Can we get 92L and 93L to sign a contract to that???

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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.
ok i see the trough has moved off the east coast and now has a 10% chance to develope, our gulf coast is safe for the moment, thanks again
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Quoting rv1pop:
I tried this in mozillafirefox and it seemed to work. Right clip on image, click on view image info, click on save image.
File type listed as .jpg, but to view it, it needs to be changed to .gif saved for me


Yeah it really is a .gif but tinypic thinks it's cute to put ".jpg" as the file ending no matter what it is.
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Quoting tropicfreak:
Am I on anyone's ignore list? Post 402 didn't deserve to be removed.
Relax... random attrition. It's happened to a few of us lately. BTW, I do suggest u stop talking to and about those trolls... that WILL cause pple to [-] and [!] ur posts...

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Quoting HurricaneDean07:
Thats the scariest Run on 92l, 93L ive ever seen!


Is there a link I can go to to see?
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Quoting Levi32:


The video run you were asking about, I see Levi posted it so he may have already made it recordable.. I tried this in mozillafirefox and it seemed to work. Right clip on image, click on view image info, click on save image.
File type listed as .jpg, but to view it, it needs to be changed to .gif. It saved for me and works
Member Since: August 18, 2007 Posts: 0 Comments: 191

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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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