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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1109. pottery
Quoting Tazmanian:
did they drop mode runs for 92L tonight?

Have not seen any....
Member Since: October 24, 2005 Posts: 0 Comments: 24461
1108. 7544
hey is good old ems coming back around again
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Quoting tiggeriffic:
temperature in Charleston 84, humidity 79%, dew point 77, heat index at 10:30pm is 93...now i am going to bed...


Another place I will never go back to in summer........as much as I love it and Savannah. Off limits June-Sept.
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did they drop mode runs for 92L tonight?
Member Since: May 21, 2006 Posts: 5091 Comments: 115255
While 93L continues to thrive, 92L looks sickly. I think it will wait until the caribbean to develop or north of the Caribbean.

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1103. bappit
Quoting atmoaggie:
These are the places where the "got wet" indicator inside the cell phones turn red after three trips in and out of the house...

And then they want to tell you it has been immersed in water and, no, your warranty doesn't cover that.

Don't keep your AC so low!
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temperature in Charleston 84, humidity 79%, dew point 77, heat index at 10:30pm is 93...now i am going to bed...
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1101. pottery
Quoting Grothar:


If you had read my blog this morning, you would have known that already.

That's where I got it from!
You dont think I figured that out all by myself do you??
Member Since: October 24, 2005 Posts: 0 Comments: 24461
Quoting Grothar:


If you had read my blog this morning, you would have known that already.


Someone called you a GIMP earlier...think it was TomTaylor.

I defended you though, as I always do.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
1099. liljade
Quoting bohonkweatherman:
Isolated Shower developed about 80 miles from my house but fell apart pretty quickly, there is some decent rain 200 to 400 miles west of here, Texas is a big state unfortunately, alot of the time the rains don't make it here before falling apart. I am happy some areas of Texas got rain, right now half an inch in Texas feels like a flood to us. Highs this weekend again thru next week will be 105 or above here, hopefully humidity goes down. If i am not going to get any rain I dont want any humidity. :) I hope those who say the High Pressure will not last much longer in Texas are right but I feel we won't see decent changes in Texas until September at the earliest except a day or 2 every now and then. Alot of the time here fronts do not start coming thru until end of Sept or early October. Without tropical systems though Texas will be in huge trouble IMO.
Here in League City,Tx. we are so dry that the Resturaunts aren't allowed to serve water unless it is asked for! That's pretty bad. Can't water lawns at all,fill ponds,pools,jacuzzies fines are $500.00 per offense.Feels like we could know what Hell really does feel like. LOL
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1098. pottery
Grand Cayman weather now---
Temp. 78.6F
Humid. 92%

You were saying????
Member Since: October 24, 2005 Posts: 0 Comments: 24461
1097. bappit
Quoting angiest:


Texas is a wee bit too big to lump in like that. he humidity falls off as you get to the Edwards Plateau (roughly, west of IH-35, but that's not a hard dividing line).

I find the humidity drops off after Beaumont, but then I'm from Louisiana.
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1096. Grothar
Quoting twincomanche:
idle banter?? Gosh I thought it was more thought provoking than most posts in the last couple of days.


So did I, but I guess we have to move on.
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1094. geepy86
Quoting Grothar:


Why don't you post something so we can discuss it. I have been posting images through all the idle banter and no one has mentioned any of them.

I seen them!
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Quoting tiggeriffic:


i guess i am lucky with the darker skin complextion and dark hair to help...but i will say that i don't think my hair has been dry once since sometime back in june...it is actually bout to my waist...i wear it up in a pony tail and braid most of the time...the weather has kept it pretty damp and then when i wash it, it takes hours to dry, by the time it does dry, i am back outside and it is wet again lol


When we go to Vegas, my hair is dry practically before I can get dressed! Here in S FL, it takes FOREVER!
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Quoting MississippiWx:
93L still looking more impressive:



I agree.
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Quoting caneswatch:


I have a bad feeling about this....

In all seriousness, I do really have a bad feeling about 93L.


It reminds me about Hugo and Georges in the early stages.
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Quoting TropicalAnalystwx13:


Yeah, I'm not trusting my feelings no more. Last time I listened to them, they said Don was going to be really bad.

Obviously, something isn't right.


Last time I had a bad feeling about a hurricane coming was Wilma. Look what happened.
Member Since: October 8, 2008 Posts: 14 Comments: 4553
1089. Grothar
Quoting pottery:

It's looking real sick right now.
If it cannot come back by 6:00 am, I think 93 will totally dominate.
92 has a lot of dry air to deal with.


If you had read my blog this morning, you would have known that already.
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1087. Grothar
Quoting Tazmanian:



ok whats the best IR site for 92 and 93L



Here you go. Maybe not the best, but a lot of stuff on it>


Link
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Quoting pottery:

It's looking real sick right now.
If it cannot come back by 6:00 am, I think 93 will totally dominate.
92 has a lot of dry air to deal with.




am starting too think about the same thing
Member Since: May 21, 2006 Posts: 5091 Comments: 115255
1085. drs2008
Quoting caneswatch:


So am I haha
Quoting atmoaggie:
These are the places where the "got wet" indicator inside the cell phones turn red after three trips in and out of the house...

And then they want to tell you it has been immersed in water and, no, your warranty doesn't cover that.
I vote for southern Mississippi.
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ok...time for bed...working another 12 hour shift tomorrow...will pop on and off when i can...say that 93L will be named by Sunday...92L...not sure yet...if it gets named it will be later than 93...nite all
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Quoting ProgressivePulse:



While insignificant alone, the sparse rains are chipping away at the subsidence. Looking between the lines this could be the start of that ridge finally abating the area. Saying a prayer for ya, the photos from Texas are astounding.


Thank you. It would be wonderful to see that ridge lose its grip for sure. :)
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1082. JLPR2
Lost power for two hours... sucks! I don't even want to imagine what would happen to PR's power grid if a storm passed over us.
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1081. robj144
Quoting kmanislander:


Right now it's 95% humidity outside and 80 degrees. By mid day tomorrow the only difference will be the 80 will be 93.


You sure about that? I live in South Florida, it's always more humid at night when the temp. is slightly cooler. Sometimes during hot, humid days, I swear the humidity is 90%, but it's normally only about 60 to 70% during the day.
Member Since: August 19, 2008 Posts: 0 Comments: 825
1080. pottery
Quoting Tazmanian:




do you think 92L has open up in too a open wave it sure is not march tonight

It's looking real sick right now.
If it cannot come back by 6:00 am, I think 93 will totally dominate.
92 has a lot of dry air to deal with.
Member Since: October 24, 2005 Posts: 0 Comments: 24461
Quoting caneswatch:


I have a bad feeling about this....

In all seriousness, I do really have a bad feeling about 93L.


Yeah, I'm not trusting my feelings no more. Last time I listened to them, they said Don was going to be really bad.

Obviously, something isn't right.
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1078. rv1pop
Quoting angiest:


You *assume* it is hitting the ground. ;) As dry as it has been, it could be evaporating before hitting the ground.
I was outside the other day, it was "raining" I got rain drops on my glasses, but it did not reach the ground. It was 99.7 degrees and only 22% humidity.
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Quoting Tropicsweatherpr:
The San Juan NWS is discussing tonight all about both invests but especially about 93L.

NEXT WEEK...FORECAST WILL HINGE ON TRACK OF TWO AREAS OF LOW PRES
ACROSS THE ECNTRL ATLC. FIRST LOW (INVEST 92L) LOOKING LESS
ORGANIZED AS DISCUSSED IN LATEST TROPICAL WX OTLK. SOME MODELS
ACTUALLY DO NOT GIVE THIS SYSTEM MUCH CHANCE OF DEVELOPMENT WITH
THE RELIABLE ECMWF AND GFDL JUST SHOWING AN OPEN TROUGH.

INVEST 93L LOOKING MORE IMPRESSIVE WITH A MORE CONCENTRATED AREA
OF THUNDERSTORMS. THIS SYSTEM IS LOOKING MORE LIKELY THAT IT WILL
EVENTUALLY BECOME A NAMED SYSTEM OVR THE WEEKEND. HPC/NHC
COORDINATION INDICATING THIS SYSTEM TAKING A MORE WWD TRACK WITH
HPC DY3-DY7 EXTENDED GRAPHICS INDICATING A TROPICAL CYCLONE JUST
SOUTH OF SAINT CROIX BY 12Z THU AUG 18. THE 12Z ECMWF (THE TOP
PERFORMER OVR THE PAST THREE YEARS) SHOWS SYSTEM TRACKING BETWEEN
ST. JOHN AND ANEGADA ISLAND NEXT THU WITH THE SECOND MOST RELIABLE
MODEL THE GFDL TAKING IT RATHER BRISKLY ACROSS MARTINIQUE TUE
EVENING. SO SOME NOTABLE DIFFERENCES SEEN HERE IN TRACK/TIMING OF ANY
POTENTIAL IMPACTS. FOR NOW THE HPC/NHC AND ECMWF SOLUTIONS LOOK
MUCH BETTER AS THEY MATCH UP BETTER WITH CLIMATOLOGY.

Link


I have a bad feeling about this....

In all seriousness, I do really have a bad feeling about 93L.
Member Since: October 8, 2008 Posts: 14 Comments: 4553
Quoting MississippiWx:
93L still looking more impressive:





do you think 92L has open up in too a open wave it sure is not march tonight
Member Since: May 21, 2006 Posts: 5091 Comments: 115255
Quoting Grothar:


Why don't you post something so we can discuss it. I have been posting images through all the idle banter and no one has mentioned any of them.


paying attention to em...just not sure what to make of all of it yet...it is still sooooooo early in the game...
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Quoting Grothar:


Why don't you post something so we can discuss it. I have been posting images through all the idle banter and no one has mentioned any of them.



ok whats the best IR site for 92 and 93L
Member Since: May 21, 2006 Posts: 5091 Comments: 115255
Dang, image hosting messed it up.
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93L still looking more impressive:

Member Since: July 15, 2006 Posts: 17 Comments: 10284
1070. pottery
Quoting kmanislander:
Power just went out so I have to shut down while the UPS is up. Catch you later

Hope it's a short one....
Member Since: October 24, 2005 Posts: 0 Comments: 24461
I know some were talking about it earlier. I really think that 92L is going to split. Northern portion is already heading around the periphery of the ridge. I think the southern portion of the wave and 93L will combine into one. B/A high looks to be building west with 93L and the resulting westward, WNWestward tracks.

Just my thoughts at the moment.

Evening all.
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1068. Grothar
Quoting Tazmanian:
hey guys can we plzs get back too 92 and 93L


Why don't you post something so we can discuss it. I have been posting images through all the idle banter and no one has mentioned any of them.
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Quoting mcluvincane:


sure.. imo 93L will be a carolina issue



yup
Member Since: May 21, 2006 Posts: 5091 Comments: 115255
Quoting floodzonenc:
Cool!  I am 1/8th Cherokee.  Not enough to keep me from being a wimp, though!

Quoting floodzonenc:
Hey, tigger.  You KNOW I love you, but...  are you crazy or are you training to be a NASCAR racer?  J/K  :P



i guess i am lucky with the darker skin complextion and dark hair to help...but i will say that i don't think my hair has been dry once since sometime back in june...it is actually bout to my waist...i wear it up in a pony tail and braid most of the time...the weather has kept it pretty damp and then when i wash it, it takes hours to dry, by the time it does dry, i am back outside and it is wet again lol
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Quoting Tazmanian:
hey guys can we plzs get back too 92 and 93L


sure.. imo 93L will be a carolina issue
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Power just went out so I have to shut down while the UPS is up. Catch you later
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no fish storm for 93L
Member Since: May 21, 2006 Posts: 5091 Comments: 115255
rain, in texas, is that true, has the impossible happened?
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1060. KEEPEROFTHEGATE (Mod)
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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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