African tropical wave 99L has potential to develop

By: Dr. Jeff Masters , 3:10 PM GMT on July 30, 2012

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The first African tropical wave of 2012 with a potential to develop is Invest 99L, located in the Eastern Atlantic near 9°N 36°W, midway between the Lesser Antilles Islands and the coast of Africa. Visible satellite loops show a large area of the surrounding atmosphere has a pronounced counter-clockwise spin, though there is no surface circulation. The disturbance's heavy thunderstorm activity is pretty sparse, but appears to be slowly increasing. Water vapor satellite loops show that 99L has a reasonably moist environment, and the latest Saharan air layer analysis shows that the dry air from the Sahara lies well to the north of 99L. WInd shear over the disturbance is a light 5 - 10 knots, and ocean temperatures are 28°C, (82°F) which is well above the 26.5°C (80°F) threshold typically needed to allow formation of a tropical depression.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is expected to remain light for the next five days, and ocean temperatures will remain near 28°C, according to the 8 am EDT run of the SHIPS model. The disturbance is at 9°N, which is close enough to the Equator that the storm will have some difficultly getting spinning. Most of the models are showing some slow development of 99L, with the storm reaching the Lesser Antilles Islands on Saturday, August 3. NHC gave 99L a 20% chance of developing into a tropical depression by Wednesday morning. I expect the storm will have trouble with dry air at times this week as it crosses the Atlantic, but I give 99L a 50% chance of eventually developing into Tropical Storm Ernesto sometime in the next ten days. Residents and visitors to the Lesser Antilles Islands should anticipate heavy rains and strong winds from 99L beginning to affect the islands as early as Friday night. The long-range fate of 99L is uncertain, but a trough of low pressure is expected to be present over the Eastern U.S. early next week, which would be capable of turning 99L more to the northwest.

Hot in the Central U.S.
The heat in America's heartland continued on Sunday, with Wichita, KS hitting 111°F, just 3° short of their all-time hottest temperature of 114° set on 8/12/1936. Other notable highs on Sunday:

111° Coffeyville, KS
111° Winfield, KS
110° Chanute, KS
110° Parsons, KS
109° Joplin, MO (all-time record is 115° on July 14, 1954)

The low temperature in Tulsa, Oklahoma this Monday morning dropped to only 88°F. This is the all-time warmest low temperature in the city since record keeping began in 1905. The previous record warmest minimum temperature was 87°F set on August 2, 2011 and July 16, 1980. The high in Tulsa Monday - Wednesday is expected to reach 110° - 111°, close to the city's all-time hottest temperature of 115° set on August 10, 1936.

Jeff Masters

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Quoting HurrikanEB:
just out of curiosity, is this 99L from the first round of invests? If i remember correctly it goes invest 90L to 99L and then back to 90L. Were all of the named systems so far this year from the same round, and is this the end of that round?



..if that makes sense.


This is the finale of the first round.
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114 hours, why is the gfs now killing 99L before it reaches the islands?
Member Since: March 16, 2012 Posts: 123 Comments: 7885
Southern Japan will get floods again...

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just out of curiosity, is this 99L from the first round of invests? If i remember correctly it goes invest 90L to 99L and then back to 90L. Were all of the named systems so far this year from the same round, and is this the end of that round?



..if that makes sense.
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Quoting TropicalAnalystwx13:

If anything enters the central Caribbean it will be ripped to shreds. That's all there is to it.

I'd show you guys how strong the trade winds in that region are, but the ASCAT site is not cooperating all with me today.


A buoy in the central Caribbean only had northeast winds of 15 kt. Unfortunately NDBC doesn't want to work now, but I would consider that comparably weak relative to other Caribbean trackers we've seen (i.e. Chantal in 2001).
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Quoting ProgressivePulse:


Notice #2 behind
Yeah I see it, lets see the rest of the run and know if the gfs does anything with it.
Member Since: March 16, 2012 Posts: 123 Comments: 7885
108 hours
Member Since: March 16, 2012 Posts: 123 Comments: 7885
Quoting wxchaser97:
96 hours


Notice #2 behind
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Trying to get my wife to go on an excursion to Ft. Jefferson. Someone posted the pic earlier and peaked my enthusiasm. She's not much for roughing it and needless to say, things were going "OK" till I brought up the composting bathrooms, lol.

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Quoting sunlinepr:


looks like.... anyhow the interaction with the ULL and the Dry air should slow down development....


if anything it look like that ULL is helping it to vent out abit plus that Upper Level Anticyclone that is currently forming on top of it should aid to it
Member Since: June 13, 2009 Posts: 2 Comments: 9547
Quoting Bluestorm5:
Just finished making my forecast. This is the second time I've created forecast (Emilia was first), but first time with the keys. Hope y'all like it! As for the forecast, I've created narrow cone because it's gonna stay going west/northwest most of the time until around HR 96. From there, the cone get wider. I really think 99L will be a slow organizing storm so I stick with the tropical storm forecast 120 hours from now. I didn't forecasts any farther than 120 hours because things changes pretty quickly. I do think this storm will go over the eastern edge of Hispaniola as a 70 mph tropical storm and weaken to 60 mph tropical storm before regaining strength to low Category 1 toward SE USA, but things changes pretty fast in the tropics. Again, this is not OFFICIAL FORECAST.

My forecast would be similar, only mine would be more pronounced a bit to the northwest.
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Quoting wunderkidcayman:


for now. shear will not be a problem at all for 99L by the time it get there and I don't think the trades will be too strong neither to cause problem at that timeframe

The trade winds aren't going to lower dramatically for no reason. They are forecast to be just as strong, which is why the GFS shows the system dissipating quickly once entering. The ECMWF also shows the strong vorticity associated with 99L entering the Caribbean and quickly dying.

If it goes there, it's dead.
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96 hours
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1457. Patrap
Member Since: July 3, 2005 Posts: 414 Comments: 125422
Quoting TropicalAnalystwx13:

If anything enters the central Caribbean it will be ripped to shreds. That's all there is to it.

I'd show you guys how strong the trade winds in that region are, but the ASCAT site is not cooperating all with me today.
I just tried and the site won't load.
Member Since: March 16, 2012 Posts: 123 Comments: 7885
Quoting TropicalAnalystwx13:

If anything enters the central Caribbean it will be ripped to shreds. That's all there is to it.

I'd show you guys how strong the trade winds in that region are, but the ASCAT site is not cooperating all with me today.


for now. shear will not be a problem at all for 99L by the time it get there and I don't think the trades will be too strong neither to cause problem at that timeframe
Member Since: June 13, 2009 Posts: 2 Comments: 9547
Quoting wunderkidcayman:


looks to me that the wave is being left behind with the ULL while the low takes charge and moves W-WNW


looks like.... anyhow the interaction with the ULL and the Dry air should slow down development....
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Quoting wunderkidcayman:
right before I go I what to say this I think 99L should be orange 40% or 50% at 2am and I think that it will track into the Caribbean with it being at 60-70mph TS in the E and Central Cariibean and a Cat 1 or 2 in the W caribbean turning NE towards Fl passes over weakens to a 70mph TS or a 75mph Cat 1 off the E coast of Fl and shoots NNE up the Eastern seaboard just my though on how this might play out

note stronger storm in W caribbean because of low shear and very high TCHP

If anything enters the central Caribbean it will be ripped to shreds. That's all there is to it.

I'd show you guys how strong the trade winds in that region are, but the ASCAT site is not cooperating all with me today.
Member Since: July 6, 2010 Posts: 108 Comments: 30237
78 hours
Member Since: March 16, 2012 Posts: 123 Comments: 7885
Taiwan is going to get hammered....


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Is there outflow?
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Quoting sunlinepr:
Those ULLs are interacting with both, the wave over PR and also over the invest....
Looks like some convection from 99L will be gone with that Northen ULL.... so that may slow development??



looks to me that the wave is being left behind with the ULL while the low takes charge and moves W-WNW
Member Since: June 13, 2009 Posts: 2 Comments: 9547
Quoting popartpete:
We have been focused on 99L, but what about the wave now exiting the Leeward/PR area with nothing but warm ocean ahead of it? They said if it goes to the north of PR, it could get better organized. No one seemed to predict that the wave would go so far to the northwest so quickly. I've heard as high as 20 miles per hour. It looks like it has an impressive amount of cold cloud top thunderstorms, and a surface rotation established. It seems like this storm is making a dent into the ridge. Will this be an East Coast threat? Will 99L follow its course? 99L is a giant system. If it gets going, it could really be something.


The wave is currently experiencing some rather nasty shear. Could be a last min thing in the Bahamas however, most of the vorticity is in the central Caribbean.

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1447. Patrap
Member Since: July 3, 2005 Posts: 414 Comments: 125422
1446. Patrap
Member Since: July 3, 2005 Posts: 414 Comments: 125422
1445. JLPR2
Quoting popartpete:
We have been focused on 99L, but what about the wave now exiting the Leeward/PR area with nothing but warm ocean ahead of it? No one seemed to predict that the wave would go so far to the northwest so quickly. I've heard as high as 20 miles per hour. It looks like it has an impressive amount of cold cloud top thunderstorms, and a surface rotation established. It seems like this storm is making a dent into the ridge. Will this be an East Coast threat? Will 99L follow its course? 99L is a giant system. If it gets going, it could really be something.


Nah, that's just convection probably being sheared away from the wave.

As you can see its spin is moving west in the Caribbean.


Also to note: 99L's spin is slowly getting stronger and rounder.
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right before I go I what to say this I think 99L should be orange 40% or 50% at 2am and I think that it will track into the Caribbean with it being at 60-70mph TS in the E and Central Cariibean and a Cat 1 or 2 in the W caribbean turning NE towards Fl passes over weakens to a 70mph TS or a 75mph Cat 1 off the E coast of Fl and shoots NNE up the Eastern seaboard just my though on how this might play out

note stronger storm in W caribbean because of low shear and very high TCHP
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Quoting Bluestorm5:
Thanks :)
Your welcome
66 hours
Member Since: March 16, 2012 Posts: 123 Comments: 7885
I have been fascinated with hurricanes/ tropical cyclones since I was 16yo and Fran hit in my back yard. That being said, as much as I would love to see 99L do well, I am not sure the good ole US of A could stand to see am major storm impact it this year or in the next few years to come. So with that being said I want to see this storm form and grow and then go back to sea.
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Quoting sunlinepr:


Wow,what a split. We may get some rain from tail.
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1440. Patrap
..thel is a wise owl fer sure.

"Trends" first, then Consensus, then we worry.
Member Since: July 3, 2005 Posts: 414 Comments: 125422
We have been focused on 99L, but what about the wave now exiting the Leeward/PR area with nothing but warm ocean ahead of it? They said if it goes to the north of PR, it could get better organized. No one seemed to predict that the wave would go so far to the northwest so quickly. I've heard as high as 20 miles per hour. It looks like it has an impressive amount of cold cloud top thunderstorms, and a surface rotation established. It seems like this storm is making a dent into the ridge, following it, but shoving ahead. Will this be an East Coast threat? Will 99L follow its course? 99L is a giant system. If it gets going, it could really be something.
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Quoting wxchaser97:
I think it is a good forecast and I believe it will follow a similar path.
Thanks :)
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Quoting JLPR2:


Didn't mean that, I know you weren't. :)

What I meant to say was that the track was in line with climatology.
I know :)
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First let me say, I personally have no desire to know ANYBODY'S sexual orientation in this blog...... please do us all a favor, and KEEP IT TO YOURSELF! No matter what your preferences!

Ernesto (2006) could follow a similar path in 2012.....



One thing for sure, at this point, it would seem likely that 99L is destined to become a named storm.......

As for track/intensity....... way too early! As some astutely commented, at THIS point, we are looking for "trends" in the models.......
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Those ULLs are interacting with both, the wave over PR and also over the invest....
Looks like some convection from 99L will be gone with that Northen ULL.... so that may slow development??

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I forgot about the 00z gfs is running, 48 hours
Member Since: March 16, 2012 Posts: 123 Comments: 7885
Quoting Bluestorm5:
Wasn't trying to copy, lol. I was just trying to show it going WNW for first 96 HR, slowly curving it to NW at 120 HR.
I think it is a good forecast and I believe it will follow a similar path.
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Storm in 4 days.... That will be maybe tomorow...

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1431. JLPR2
Quoting Bluestorm5:
Wasn't trying to copy, lol. I was just trying to show it going WNW for first 96 HR, slowly curving it to NW at 120 HR.


Didn't mean that, I know you weren't. :)

What I meant to say was that the track was in line with climatology.
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1430. Patrap
Yer eye's are bad old Hinge
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Quoting JLPR2:


It is interesting that is your forecast, check CLIP5, which is a climatology based model.


Pretty much the same, lets see if climatology wins.
Wasn't trying to copy, lol. I was just trying to show it going WNW for first 96 HR, slowly curving it to NW at 120 HR.
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1427. Grothar
Quoting Patrap:
00z Early Cycle NHC model tracks
Invest99

Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Dynamic Models (More sophisticated models)




Early Model Wind Forecasts



Pat, are you losing it. Why are you posting tracks for Chris????
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Well I just checked in to see what condition my condition was in, and it looks like I'm in good hands.

Once again, The Blog is spinning in greased grooves...

'Nite All
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Quoting TropicalAnalystwx13:

Well that's not where it's going so you should be happy.
too.far.out.to.say.that
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Quoting Bluestorm5:


It's a big question mark, but I do think this storm will go over the eastern edge of Hispaniola as a 70 mph tropical storm and weaken to 60 mph tropical storm before regaining strength to low Category 1 toward SE USA, peaking it at 80 mph. Things changes pretty fast, though so consider it a low confidence forecast.
I read your full statement and saw that answered and I edited my post. Thanks for posting it again though.
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Quoting HurricaneDean07:

Maximum intensity for this storm is Category 2. If it can cleanly get away from the caribbean islands...
If it goes through the caribbean it should only reach 60 mph TOPS. and if it goes through the northern caribbean islands it might get to 70 mph.. might not.

Id say it has a 10% chance of a cat 2
30-40% cat 1
60% TS
80% td in the next 5 days
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Quoting islander101010:
dont.want.99.in.the.nw.carib.or.gulf

Well that's not where it's going so you should be happy.
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Quoting wxchaser97:

Right around my forecast:
img src="">
How strong do you think 99L will get Blue?


It's a big question mark, but I do think this storm will go over the eastern edge of Hispaniola as a 70 mph tropical storm and weaken to 60 mph tropical storm before regaining strength to low Category 1 toward SE USA, peaking it at 80 mph. Things changes pretty fast, though so consider it a low confidence forecast.
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Overall:
I give 99L a 65% chance of formation into a tropical cyclone...
and a 40% chance of it forming within the next 48 hours.
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.