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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1058. Grothar
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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
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1056. pottery
Quoting yesterway:


Take it up with the NWS.

Me?
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hey guys can we plzs get back too 92 and 93L
Member Since: May 21, 2006 Posts: 5091 Comments: 114703
Quoting Grothar:


Depends on what part. Central and Northern Florida can be brutal in the summer. I mean we are not Death Valley, but it depends on where one is in Florida. The more South you are the milder the summer. It can be very humid here at times. But I have been to Georgia and Louisiana in the summer and it was much more humid there.


Being a S FL native, I can say that we may be a bit cooler than Central & N FL. I am guessing it is b/c of the sea breezes and then PM thundershowers off The Lake that cool things off. You can't pay me to go to Disney June-Sept. Too hot and humid. However, I find the heat in Vegas at the end of May-early June just as stifling--just not suffocating. Dry heat is still heat--106 on June 6th. And the breeze is HOT, too! We will not go to Vegas June-Sept. either!!!!! Contrarily, it is almost too COLD to go to San Fran and/or Yosemite in May!!!! Yellowstone in 2012 in mid-May may even be a mistake for this Florida-girl!
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Quoting pottery:

Well, you need to get to one of these Islands after a Hot morning, and the sky falls at 2:00pm and the roads are visibly steaming....
Believe it, it happens. Often.


Take it up with the NWS.
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Quoting AtHomeInTX:
Evening everyone. This has got to be the most optimistic local forecast I've seen in a while. Keep in mind our "higher rain chances" are 10-20%. And they're talking about a storm off the coast of Africa. But HEY ya never know. :)


Higher rain chances this weekend...

By Patrick Vaughn

Upper level high pressure is expected to shift west and weaken over the course of this weekend. At the same time, a trough of low pressure will move through the Mid-West. This will enhance shower/thunderstorm activity over this weekend...especially Sunday. Then, next Tuesday the upper-high will begin building over the region. Temperatures will go up, but so will rain chances again as moisture move along the eastern side of the high into our area.

In the Tropics, two areas of concern are in the far Eastern Atlantic. Both of these systems are expected to develop and could become Franklin and Gert. The first system, is further north and is forecasted by the European to be a "fish" storm...never making a landfall. However, the second may be a bit of concern as it is further south and forecasted to move just north of the Caribbean Islands. The verdict is still out on this one on whether on not it will reach the Gulf.



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.
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Quoting floodzonenc:
Cool!  I am 1/8th Cherokee.  Not enough to keep me from being a wimp, though!



So am I haha
Member Since: October 8, 2008 Posts: 14 Comments: 4553
1050. KEEPEROFTHEGATE (Mod)
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1049. pottery
Quoting yesterway:


Your temp and RH are off the charts. Those kind of numbers just don't happen. More like 94 degrees and 55% RH...

Well, you need to get to one of these Islands after a Hot morning, and the sky falls at 2:00pm and the roads are visibly steaming....
Believe it, it happens. Often.
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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.


LOL...I've never thought about that before now.

But yeah, the humidity here in South MS is a killer, but anywhere close the GOM is going to be extremely humid in the summer.
Member Since: July 15, 2006 Posts: 17 Comments: 10159
1047. Grothar
Quoting kmanislander:


HUH ??. From noon until 6 nothing but T & L, dark clouds and rain. .42 inches in South Sound but quiet as a church now.


Is it humid where you are?
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1046. angiest
Quoting mcluvincane:


LOL.. I know, just joking around. I love Texas myself. I visit Houston quite often. The Woodlands


A little north of Conroe, there was a recent fire that burned through the pine forest. Jumped over IH-45.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting yesterway:


Your temp and RH are off the charts. Those kind of numbers just don't happen. More like 94 degrees and 55% RH...


Right now it's 95% humidity outside and 80 degrees. By mid day tomorrow the only difference will be the 80 will be 93.
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1044. Grothar
Don't know if this was posted already, but the GFDL really moved more West on the last run with 93L

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1043. KEEPEROFTHEGATE (Mod)
XX/INV/93L
MARK
12.35N/28.00W


XX/INV/92L
MARK
15.85N/39.89W




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Quoting txjac:


Hey now ...we sit here pretty quiet when all the Florida people talk about all the lovely rain they are getting ...and we will be quiet and worry when storms come everyone's way ...just happens that there are a few of us here tonight commiserating (spelling?)


LOL.. I know, just joking around. I love Texas myself. I visit Houston quite often. The Woodlands
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1040. pottery
Quoting kmanislander:


Still no heavy flooding rains here this year, not that we want any. Before the year is out we will likely have a deluge or two, it never fails.If a TC comes this way then several inches in a day or two would be pretty much a certainty.

July 26 th was our last HEAVY shower.
Only lasted about 40 mins, but 1.5" came down with a fury!
Shook this old house to the foundation at times.
Nice!
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Quoting kmanislander:
High heat and humidity is a fact of life in the tropics. 94 degrees of heat and 96% humidity is pretty common here from June/July until November.

We use airconditioning for everything, from the home to your car and then into work. Very little time is spent outside in the elements during the work week unless it can't be helped.


Your temp and RH are off the charts. Those kind of numbers just don't happen. More like 94 degrees and 55% RH...
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Quoting txjac:


Hey AtHome ...hope all is well with you.
I gave up wishing on rain ...just wish for clouds now!


Hey TXJ. I'm ok. Hope all's well with you. And I did about the same. I'm just waiting for the dry air to be cooler. Lol.
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Just finished listening to the hurricanehollow livestream, and Levi- excellent job talking about the tropics.

Joe B is so incredibly lame. Misses an opportunity for an interview and instead, tweets a bunch of useless information.

But regardless, great job Levi!
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Quoting TropicalAnalystwx13:
My top-5 most humid places:

1.) Mississippi
2.) Pressolina
3.) Florida
4.) Louisiana
5.) Texas
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.
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1035. geepy86
Quoting Grothar:


Would you like to try that in my neighborhood?

Well, really most my neighbors are hung over, so they never hear me.
I forgot I use horses and sheep for the mowing.
: P
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1034. txjac
Quoting mcluvincane:
Seems like a Texas style blog tonight. zzzzzz


Hey now ...we sit here pretty quiet when all the Florida people talk about all the lovely rain they are getting ...and we will be quiet and worry when storms come everyone's way ...just happens that there are a few of us here tonight commiserating (spelling?)
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Quoting SubtropicalHi:
Quoting Neopolitan
Weather Historian Christopher Burt has an excellent blog post on dew point temps. Talk about some very uncomfortable humidity:

"The absolute highest dew point recorded in the region and therefore the world (of which I am aware) was 95.F at Dhahran, Saudi Arabia at 3 p.m. on July 8, 2003. The dry bulb temperature stood at 108.F at the time, so theoretically the heat index was 176.F. Sharjah in the United Arab Emirates (UAE) apparently once recorded a dew point of 93.2.F (date unknown) according to 'Weather Climate Extremes' Army Corps of Engineers TEC-0099 report



UAE has the worst of heat & humidity combined. It almost makes Texas look "pleasant"
That is Unheard of, Wow
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Quoting Grothar:


Child, what it wrong with you?? The first words that babies speak in Florida isn't Mama or Papa. It's "Turn up the air-conditioning." How do you stand it without A/C in a Car. At least in my day we had covered wagons and got some air.



I honestly don't know how I am surviving w/o the AC... You can bet on it as soon as I get the money I will be getting that thing fixed
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Quoting stormwatcherCI:
????? Sure didn't see any up here. Not even a cloud in the sky. You need to share :)


HUH ??. From noon until 6 nothing but T & L, dark clouds and rain. .42 inches in South Sound but quiet as a church now.
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1030. Grothar
Quoting geepy86:

Hah, I mow my yard at 6 (am)
My neighbors aren't happy, but it is cooler.
: )


Would you like to try that in my neighborhood?
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Quoting Neopolitan
Weather Historian Christopher Burt has an excellent blog post on dew point temps. Talk about some very uncomfortable humidity:

"The absolute highest dew point recorded in the region and therefore the world (of which I am aware) was 95.F at Dhahran, Saudi Arabia at 3 p.m. on July 8, 2003. The dry bulb temperature stood at 108.F at the time, so theoretically the heat index was 176.F. Sharjah in the United Arab Emirates (UAE) apparently once recorded a dew point of 93.2.F (date unknown) according to 'Weather Climate Extremes' Army Corps of Engineers TEC-0099 report



UAE has the worst of heat & humidity combined. It almost makes Texas look "pleasant"
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1028. txjac
Quoting AtHomeInTX:


I know that is making a lot of people happy right now. I'm happy for them. :)


Hey AtHome ...hope all is well with you.
I gave up wishing on rain ...just wish for clouds now!
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Seems like a Texas style blog tonight. zzzzzz
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Quoting Ameister12:

I'm sure that Texans are thinking very differently.


I know that is making a lot of people happy right now. I'm happy for them. :)
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1025. Grothar
Quoting pottery:

Strange you should mention Pott and Luck in the same breath.
Had it for supper.

The Beverage was fine.....


You don't miss a thing.
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1024. angiest
Quoting tropicfreak:


That's going to put a dent in the drought, those storms aren't going anywhere fast!


You *assume* it is hitting the ground. ;) As dry as it has been, it could be evaporating before hitting the ground.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1023. pottery
Quoting Grothar:


That little island of yours isn't that big. I can find you. LOL How you doing pott? Any luck? hehehe

Strange you should mention Pott and Luck in the same breath.
Had it for supper.

The Beverage was fine.....
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Quoting kmanislander:


LOL. Actually we got quite a bit today with lots of T & L. Purely a local event that barely showed up on satellite but very impressive to see. I witnessed several significant lightning discharges over the cruise ships in harbour and then later ( around 6 our time ) over my neighbourhood.

You certainly didn't want to be outside holding an umbrella !
????? Sure didn't see any up here. Not even a cloud in the sky. You need to share :)
Member Since: October 9, 2008 Posts: 0 Comments: 8266
1021. angiest
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.


"Oh there's floodin' down in Texas, all of the telephone lines are down..."
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting AtHomeInTX:


Sounds like here. Only no one spends time outside at all during the summer unless they have to. Moving is like swimming in syrup. I can't wait til the first rare cool front comes through. :)


Well, there is golf on the weekend though when the heat and humidity are just fine. lol
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1019. geepy86
Quoting tiggeriffic:


lol...i am in Charleston, SC...and unless my little one or husband is with me, i don't use the a/c in my vehicle...i roll the window down and open the back opera windows...been pretty hot here too...heat index in the 110+...lots of heat advisories...and i will even mow the lawn in the middle of the day...

Hah, I mow my yard at 6 (am)
My neighbors aren't happy, but it is cooler.
: )
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1018. Matt74
Quoting AtHomeInTX:
Evening everyone. This has got to be the most optimistic local forecast I've seen in a while. Keep in mind our "higher rain chances" are 10-20%. And they're talking about a storm off the coast of Africa. But HEY ya never know. :)


Higher rain chances this weekend...

By Patrick Vaughn

Upper level high pressure is expected to shift west and weaken over the course of this weekend. At the same time, a trough of low pressure will move through the Mid-West. This will enhance shower/thunderstorm activity over this weekend...especially Sunday. Then, next Tuesday the upper-high will begin building over the region. Temperatures will go up, but so will rain chances again as moisture move along the eastern side of the high into our area.

In the Tropics, two areas of concern are in the far Eastern Atlantic. Both of these systems are expected to develop and could become Franklin and Gert. The first system, is further north and is forecasted by the European to be a "fish" storm...never making a landfall. However, the second may be a bit of concern as it is further south and forecasted to move just north of the Caribbean Islands. The verdict is still out on this one on whether on not it will reach the Gulf.
He's okay but i like Bostwick better.
Member Since: June 21, 2011 Posts: 0 Comments: 329
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



lol floodzonenc...not crazy, ex navy...lol...talk about hot in those bunks!!! and the machine shop where i worked was worse...i do sweat some when outside but it doesn't get to me as fast as it does the rest of my crew lol...and i guess it helps that i am part cherokee...my mom tolerated the heat well too...
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Quoting pottery:

Well, I am complaining about lack of rain so far in Aug.
But JUNE was one of the wettest ever.
Measured rainfall on 22 days.....

Tapered off, mid July.

edited


Still no heavy flooding rains here this year, not that we want any. Before the year is out we will likely have a deluge or two, it never fails.If a TC comes this way then several inches in a day or two would be pretty much a certainty.
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Quoting kmanislander:
High heat and humidity is a fact of life in the tropics. 94 degrees of heat and 96% humidity is pretty common here from June/July until November.

We use airconditioning for everything, from the home to your car and then into work. Very little time is spent outside in the elements during the work week unless it can't be helped.


Sounds like here. Only no one spends time outside at all during the summer unless they have to. Moving is like swimming in syrup. I can't wait til the first rare cool front comes through. :)
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Quoting Ameister12:

I'm sure that Texans are thinking the exact opposite.


That's going to put a dent in the drought, those storms aren't going anywhere fast!
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Quoting txjac:


I was wondering if you got any of that rain that appeared to be falling in west Texas ...guess not, sorry
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.
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1012. txjac
Neo ...where the heck to you pick up all of these interesting tidbits to entertain us with? Between you and Skye ...always something interesting and entertaining ...thanks
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1011. Grothar
Quoting pottery:

An OLD bone thats been on the driveway for months....
No wisecracks needed, by him......


That little island of yours isn't that big. I can find you. LOL How you doing pott? Any luck? hehehe
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Quoting WeatherNerdPR:
AT LONG LAST
No rain :D

I'm sure that Texans are thinking very differently.
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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.